> So it happened again. One of my questions has been closed inadvertently. The folks who have closed it claimed that it is not about hardware as outlined in the help center.

There isn’t anything inadvertently about the close vote I issued.   The question was asking a question that only the manufacturer in question can answer. 

> There are dozens of questions which are nearly literally like mine, or very similar. 

Those examples only asked if the hardware was compatible or incompatible.  You were asking if the documentation, which is the documentation anyone in this community would use to answer that question about your hardware, was actually correct or incorrect.  You also wanted to know the reason the documentation was correct or incorrect.

> So why the heck has my question been closed?

The only reason I had was due to the fact you asked the reason the documentation was correct or incorrect.  Questions asking the reason a manufacturer has made something incompatible or compatible is impossible to answer.  While your edit clarified what you were looking for, you never removed that part of the question, which might have resulted to in the question being reopened.

> The first time the mod who closed it showed a very mature behavior by reopening it although I had a little dispute with him due to the close where I was behaving immature and possibly insulted him (at least, I chose inappropriate wording).

This only is evidence of our excellent moderator team treating everyone the same.

> I think I'll leave here forever and give others the same advice if the situation is not resolved. There are only a few things which are more frustrating than (being a non-native speaker) carefully crafting a question which clearly adheres to all site policies, doing your own extensive research before, checking the question for orthographic and errors and correct wording, and then having it inadvertently closed.

I am not sure you understand what inadvertently actually means.  I purposely issued a closed vote due to what you were asking.  You wanted to know something I thought only the manufacturer could actually answer.  *Using my best judgment I avoided a discussion about my vote by not leaving a comment purposely.*

However, my single vote to close your question, is exactly that a single vote.  Only moderators have binding votes.

> So I hope somebody with enough power reopens that question or explains in detail in which way it is off-topic. Only claiming that it is off-topic because it is not about hardware is not a sufficient explanation, because it obviously is about hardware.

Since you question the accuracy of the documentation, there isn’t any way the community can answer your question, which is the reason you should contact the manufacturer.