oh, sry my english bad, but i try answer more correct.
I`m using wakaba 3.0.8.

Problem in any wakaba marks, which applies to url link.
news, irc, http, https, mailto.
User can include code, wich end of code her post.
Its starting as: irc:</blockquote> and some next end-tags of post.
And in this wakaba not filtered it. In result after end-tags, you can include starting-tags for new post - and in results it will be double-post like a 2 or more messages.

I was forced to disable all marks(news, irc, http, https, mailto), because hackers have more fantasy and did all threads in only 1!! omg.

sry for bad english, but i hope you anderstand what i mean.