[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.)