Sparked by the discussion about the Hitler-Stalin Pact by a Dutch historian called: "Bedrogen bedriegers" (arroseurs arrosés) (they translate by: to get a taste of one's own medecine)
I wondered how difficult it is, even for a real historian to stick to his research without bias, especially when he is already part of a culture or a national perhaps nearly official country narrative?

Perhaps have I personally had not the same curriculum as many, as we coincidentally in the six years classic studies had teachers, who, at least some as the teacher of history, were a bit against the beaten paths of the "official" history. And then I from house out, with very critical parents against politics and political movements, which wanted to explain reality along their preconceived theorems.

For instance to give some examples of my experience...

While it is now the 200 years since Napoleon's death, there is again a lot to do about Napoleon:
https://www.euronews.com/2021/05/04/napoleon-why-is-it-controversial-to-mark-200-years-since-the-french-military-leader-s-deat
I was on a now nearly dead French forum of world history linked to a specific forum about Napoleon. As I have not enough knowledge about the typical history of the Napoleon era, I contributed nearly all my messages on the world history forum, most on WWII. 
But I felt that when I spoke about the French occupation of the then Austrian Netherlands, I found that my French counterparts saw it not the same way or were perhaps too polite to contradict me.
Perhaps they could have said that the Austrian Netherlands were also an occupation, although in my opinion they were heritated along the then European monarchial system...
Also on the French forum Passion Histoire I have the impression reading between the lines that there are still a lot of admirors and some who want to (smooth over?) his controversial deeds...

As the Orangists in the nowadays Netherlands are nearly a faction as in Nothern Ireland (hmm, perhaps not that strong and more a ladies' royalty faction) and always speak about their kings, as if they existed already from William of Orange, I remember them that it was only William who became king in 1815 thanks to the British government and that it was till then a Dutch Republic, only interrupted by the French "occupation"...

When a nowadays Flamingant boasts about the centuries long great history of "Flanders", I remember him that the nowadays Flanders as a federal state of the nowadays Belgium, only has its roots from the Flemish movement starting in the seventies of the 19th century and the before Flanders was always been the County of Flanders starting in the 12th century...
And I remember them that the idea of the nowadays Belgium in the territorial, cultural and sociological sense, existed already from the separation and partition of the then seventeen original Burgundian provinces of the Netherlands (what the English mostly call "the Low Countries") during the 80 years war
https://www.britannica.com/event/Eighty-Years-War

When an historian is accused of "bias" the charge can often be easily demonstrated. However what is not so easy to demonstrate is the equal liability for bias to reside in the mind of the reader, not the writer, and the only guilty party in the whole exchange is often simply the limitation of language itself.

Take your own honestly expressed and factually correct sentence:
... before Flanders was always been the County of Flanders starting in the 12th century...

To an Irish or British reader the use of the word county denotes an administrative area within a centralised monarchical structure (or later constitutional democratic structure) in which power typically devolves or is delegated using a hierarchy of titled positions unrelated to that which lent its name to the area itself. Counties do not require counts, in other words, and even when they have one the count himself has an implicit subservient role within a tightly integrated chain of command.

In the rest of Europe however a county may enjoy equal association with a count, as in Britain, but what distinguishes a count from the rest of aristocratic titles is that they traditionally derived authority often from a third party outside the immediate power structure as represented by the local monarchy, for example the Holy Roman Empire, or even inherited from a now defunct polity which had yet to be totally assimilated into the newer regime and enjoyed a large degree of autonomy as a result.

So your sentence, depending on the reader, could be taken to imply that Flanders had a long history as an administrative district within someone else's overriding power structure, as an area with sufficient autonomy traditionally to influence the conduct of such power structures in which it incidentally found itself, or even an area defined by a traditional autonomy which always owed ultimate allegiance to an authority quite outside that power structure entirely. What is to be inferred regarding Flanders' modern inclination to independent conduct changes fundamentally depending on which of the above scenarios is assumed by the reader based on your words. Likewise what the reader assumes your intended point to be, and consequently your own potential bias, is equally influenced by this original interpretation of your use of language too.

So, Flanders and counties aside, one can see just how easy it is to imply or assume bias where in fact there was none, or where maybe quite another bias was actually intended, and where neither the writer nor the reader was even conscious of the process whereby this confusion or misinterpretation arose. Linguistic limitation leading to semantic inexactitude and unconsciously subjective interpretation is a pitfall in any written communication but one which particularly applies to history - a subject which by definition deals with semantics and concepts that themselves have altered over time, even if the word used to convey them at times hasn't.

Yes nordmann you can be right about the semantics, and it is perhaps even more difficult, when one tries to expand on a question in another language of that were the question is discussed. And yes some bias can be emerge in the mind of the reader, listener, as it is difficult to interpret what that reader understands under the head of concept of the words that one uses, especially in another language.

And yes my example about "Flanders" was originally among Flemings. In the example it were three: a notary, a "Flamingant" and I...in a "café"...
https://en.wikipedia.org/wiki/Flamingant
(as an aside: I learned today that there was already "Flamingantisme" from the French occupation of the Austrian Netherlands and not as I presumed caused in the second half of the 19th century in reaction to the French speaking elite in the Dutch dialects speaking Northern provinces of the new Belgium of 1831)

In the café, the Flamingant boasting to the notary about the realisations of the new Flanders, which more and more proved that they were on the road to play the dominant role in the nowadays Belgium. I on the next table and knowing the notary and when we three left the café, I couldn't resist (as from my youth also a Flamingant due to my family, but as my family, become by critical enquiry more universal minded) to claim that the nowadys Flanders is only a political concept that is created in the 19th century by the Flemish movement and had nothing to do with the original "Flanders" as it incorporated now the former province of Brabant and Limburg (part of the Prince-Bishopric of Liège).
A bit as the pars pro toto, as Holland for the Netherlands, or indeed Flanders for the whole North of Belgium...
I agree that it was not nice from me and a bit teasing because of the bombast of the Flamingant...
But all of us three were quite aware about what I speaking about and didn't misunderstand the concept of my words, the notary that I knew quite pleased and a bit laughing and the guy as we left! a bit "groen lachend" (they translate: gallows humor) and no café incident...

But nordmann that aside, I think that I understand what you mean and I thank you for that.

I don't know if I apply now my new formed knowledge rightly, but to take now the figure of Napoleon. For one reader Napoleon will be a nearly mass murderer, who sent hundred thousands soldiers to their death for a wrong cause and for other readers it will be the famous emperor who made France great on the world stage.
But when an average reader compares with for instance Caius Julius Caesar, one can perhaps apply the same criteria to Napoleon and as Caesar nowadays is still glorified for his deeds of 2000 years ago it is perhaps also obvious that the French general Bonaparte of the end of the 18th century...

Kind regards, Paul.