Occasionally when posting a comment I find that the @username that I generally put at the start gets dropped when I save it. This is normally correctable by editing and re-saving the comment. Somewhat annoying but not the end of the world.
Tonight I was posting a comment to this question and despite twice editing and re-saving it, the "@Frerich" that I was trying to put at the beginning just kept getting dropped. I gave up at that point.
Using Google Chrome version 22.0.1229.79 on OS X 10.8.2 (Mountain Lion), with all updates applied.