that extension, although not really neccessary, will help with SEO a lot more than "friendly urls" would.
however, I do not agree that it should be in the core. not everybody cares about SEO for their boards. I would be willing to bet that the majority of boards have no real use for SEO ( even if the owners think they do ) .
the main reason for worrying about SEO is if you are trying to sell something on your board.
of course, the best way to sell things is to get as many visitors as possible but, the best way to sell things online is not with a bulletin board to begin with.
nothing needs to be in the core other than core code for a bulletin board.
all the rest should be extensions as it already is.
remember, this is just my opinion just as your post is just your opinion.
and you know what opinions are like.....