For these, we do have some protection with the edit window limits (more stringent for lower trust levels, but most sites keep the default 30 days for TL2+), but I think human spammers can be wise to a lot of the tools over time and more so as Discourse becomes more popular.
We had one here just the other day that the auto-tools didn’t catch who came back and edited a hyperlink into a full stop in their innocuous looking post. They can be real sneaky.