Hi Kazerniel

I was made aware of the post the day that it went up. I decided against putting a curation up mainly for the reasoning of it not fully matching something we would normally cover since we usually only cover stuff that hasn't already gotten a lot of attention prior and also with the fact the developer retracted his comment shortly after the post to r/steam was made. However due to requests from some users, I think a curation will be made but a comment will be included stating the comment put on the review was retracted later on.

As for your question, I believe it's correct only developers can flag the reviews, it may be possible that forum moderators can flag reviews as well although personally I haven't seen an instance of this being the case. However seeing as how on the image it states it was flagged "by a developer" it's safe to assume the developers were behind the flagging.

The review can't be pulled from public view by the developers however as the flag has to be reviewed by Valve or a Valve moderator for it to be taken down.

I see, thanks! (I found the original review later, and added in an edit.)

Developers can only flag(meaning report) reviews, only Steam global moderators can then check that flag and ban review if they think it's justified (which is kinda rare).
So devs can't hide reviews on their own.