I noticed that 2 threads about DJI Avata are no longer visible in the DJI FPV Forum.

Why?  Because they get sorted to the end of forum at Page 33 - regardless of whether you picked sort by Latest Replies or Latest Post.
One thread had replies just a few hours ago.
So even though they have not been deleted, but they are effectively hidden from view for most users.
They do show up in search.

And it looks too much of a coincidence for a bug to happen to 2 threads.
So is this intentional to hide the posts from users?

I would prefer a clear guidelines as there is no indication that the thread was not welcomed judging by the replies of DJI staff in each post.

Interesting that your thread got moved to last page without any type of reply from a DJI Mod/Admin.  Guess they have opted to not answer you question.

Seems odd that the Mini 3 was discussed numerous times in the forum before it's release but now the rumored Avata discussion is not being allowed.  

Bit of a shame as it does create interests in the upcoming mini FPV and definitely will help with sales as more and more people get excited for it's launch.