To each their own.. the performance hit is negligible, imo..
You actually get a HUGE performance increase, depending upon what you are doing..
Example is to split the ubbt_POSTS table up into 2.. 1 ubbt_posts_archive is in another DB (for archived posts) then the normal ubbt_POSTS table stays as is.
Modify ubbt_TOPICS to then have TOPIC_STATUS include a new type 'A' for archive..
then in normal day to day operations, the ubbt_POSTS table is being queried with MUCH less records to retrieve for cfrm and postlist..
only time you would hit up the ubbt_posts_archive table would be for searching or showflat (if archive)..
it's like night/day in performance increase
so i see your point, and believe your example holds for things like extra field in ubbt_USER_PROFILE or whatever.. but there are really quite a few tables where splitting them off would actually increase the speed..
so i guess we agree in some way too