Hmm … actually, you’re right … pretty sure I’ve replied to my own replies in the past too … yet I have a recruitment thread on my realm forums, and have been unable to reply to it using the same character (but can using the same account with a different character). I’ll have to experiment, but it would be great if we could find out the exact rules … and whether or not we should be able to reply to our own threads.
edit … I tried to reply to this post and got the standard “please wait until someone else replies” message