I don't understand the BB code part. I think the dir thing is a good idea, but the BB code is stupid and just adds another step in the HTML parsing (since you have to parse it then give it to the HTML parser).
If you actually look at it, all the functions can be easily changed:
[b] -> <b>
[i] -> <i>
[u] -> <u>
[img] -> <img src="url">
[center] -> <div align="center">
[right] -> <div align="right">
[justify] -> <div align="justify">
[color=?] -> <font color="#RRGGBB">
[bgcolor=?] -> <body bgcolor="#RRGGBB">
[size=?] -> <font size="+n">
http://blah.com))] -> <a href="url">
I understand that in BB code the functions are slightly more abstracted, but in HTML it is so much more powerful and it doesn't waste the resources adding a plugin does. Either way, someone that doesn't know BB code would either have to learn it or just learn the proper thing, HTML.