Chatbox text changes

Sometimes the text in chatbox goes bold or underlined. Why is that and can it be fixed?

Without any bbcode being used?

Er yeah... I think so. I mean if the users can't change everyone's text then yes.
If one of the users changes their text can it affect everyone's?
It's not only the 'spoken text', the usernames get underlined and bold aswell.

It's not that big of a problem but if there's a way round it I'll be glad to know about it.

I don't think if one uses the bbcode, others text should get affected in any way.
Maybe you should do a /cls then check what happens.