For the benefit of any other readers of this page, here is the problem:

Stream of vandalism-only accounts being created. See user creation log, search for 'Lesbianism'.

These four accounts were created over a period of one minute.

If this starts up again, it is possible to ask a checkuser to block the underlying IP from which the accounts were being created. This particular vandal may have got bored, so I didn't pursue the matter any further. I no longer know any checkusers who are often around.