If you use any tag like [size] or [font ] than it wont work unless you put at the end a [/font ].....Shouldnt this be like plus! where if u dont close the tag the foramt is applied till the end of the post? Just kinda...bothered me

It's kinda to prevent the situation that if I use a [u] tag but forget to close it, the <u> tag (which is transformed from mycode to html code) would just never stop until it meets a </td> or other </closetag>. Hm, and my post would look screwed up

Yeah, what Mnjul said.

Also, BBCode is based on HTML, and actually converted into HTML by the post parser... HTML always has closing tags, unless the coder sucks.