@mentions don't work for me, no auto-complete, nothing. Rather annoying when you really want to point at someone.
I've tried variations of browsers, plugins, safe-starts .. no go. So, I decided to start doing it manually.
For those with a similar problem there is a work-around. @mention is simply a board code similar to those quick inserts above the message box.
Look at a users profile link, it has a number in it, copy the number place it in the tags, like so:
[member=####]NAME[/member]
Mine looks like this:
[member=56463]Faith[/member]
the result is this:
@Faithsorry if this is shared elsewhere, I've seen the question come up regularly.