If a scammer posts on someone else's thread then the creator of that thread or anybody else can post a warning.
ok maybe i should have explained my concern a bit more.
1- a scammer starts a locked thread selling gift cards.
2- uses a sockpuppet to comment saying he sells the same gift cards maybe at cheaper rate and posts his email/telegram contact.
3- another sockpuppet to vouch for the previous sockpuppet.
4- another sockpuppet to confirm the scam warning about OP and vouch for the first sockpuppet.
This is just one of many other scenarios, i am all about optimism but i can't ignore the fact this move alone won't help newbie visitors the way we expect.
you know scammers don't rest, it's pretty obvious that this will be their next strategy, so in order for us to keep fighting them, surfing topics alone will not be enough, we now have to dig into every reply.
@sandy has got a lot of work to do now since this was her idea

What you describe would be off topic. You should report those posts and they should be deleted.