There is currently no method to flag a user account as spam (only posts). However, there is a huge influx of user accounts that are clearly spam (look for the "Autobiographer" badge on the home page, and it typically has multiple rather oddly - and often offensively - named accounts whose "About" page is an advert for a commercial product completely unrelated to mathematics or any neighboring discipline).
If feel that it would be highly desirable to be able to flag such accounts for deletion. Hence the present feature request: Could such a tool be added, please?
(Cf. also Flagging spam user, How to report intrisically spammy user accounts?)