[apologies if this is an old suggestion]
We're seeing a spammer who is persistently vandalizing multiple
pages with a certain URL. The URL is on the blacklist, so the
spammer is now just spelling it out, without any hotlink markup.
See [[Wikipedia:Administrators' noticeboard/Incidents#Ref desk spam]],
See [[Wikipedia:Administrators' noticeboard/Incidents#Anontalk spammer]],
and [[Wikipedia:Village pump (technical)#Making various types of
spam/vandalism that little bit more difficult]].
I realize there's an infinite-regress cat-and-mouse game here,
of which a "plaintext" link blacklist implementation is just one
more step, but it seems it might be an appropriate next step.
(I have no idea what it would require implementationally, however.)