Uhm, that sounds dirrrrty!
So let's say three employees of the company X quit the company and have been active in the Bugzilla of X. Now "deleting" these three user accounts and merging them into one big "Once upon a time this was a Bugzilla user" account will make it impossible later on to see which person has written (and especially: decided) what. Unlikely that this is wanted from a company and community point of view with regard to transparency.