This seems to be a new bug on the forums, but it's very annoying.
Whenever you make a quote like |quote=| text |/quote| in any forum post (using square brackets instead), and you try to edit, it just doesn't let you edit and turns the forum post blank.

Not new at all, this has been known for years, even I reported it on the forums in May of this year and I later found out that it was nothing new.

I think it happens when the post has an open quote, which is not closed properly.
I reported it a long time ago.

It's very annoying lol

thats bbcode. We used to troll people by putting a at the end of our forum messages on steam to mess with the quoting button lol