You have to know, guys, here at BU we have also some memebers which are moderators of other boards (developers of some mods) and they are pretty inactive, too, but as I know a bit one of them (he is much nervous
) he could take this clearing/deleting his account here as something unnice (almost like some kind of banning). You understand - it's at least not political...
That's why I suggest leave it as it is or - if after contact with them - they will confirm clarly - they will not use BU acount anymore - then OK - You can delete them.