"[b][size=3][color=bb0000]Posting a reply to this message is not allowed, the reply chain can only be up to 10 posts deep. Try to post a new message or reply to a earlier message.[/color][/size][/color][/b]"
Allowing only 10 replies to a topic is a ridiculous limitation, one that [italic]no other message board software on the Internet has[/italic].
It looks like you noticed formatting issues with deeply nested threads, so you "solved" it by not allowing them to get more than 10 replies deep. This is a case where the cure is worse than the disease. You're sacrificing core functionality of [italic]discussion[/italic] software to make it easier to write some display code.
If you can't figure out to format deeply nested threads, then just don't show a tree view at all. Just show each thread as a flat view, perhaps with multiple pages, just like other board software. Or you can combine the two, like Google Groups. But simply telling us "Sorry, your conversation is done, move along" is extremely frustrating.