It's quite plausible that many MO users do not know what to do when they see spam posts. I saw people interacting with spam posts as if they were serious posts, editing them, even creating (spam) tag.

Probably making a post on meta with an explanation how the spam posts are supposed to be handled might be a good idea.

In fact, there have been several occurrences of the spam tag: https://data.stackexchange.com/mathoverflow/query/883845/deleted-questions-with-‌​a-given-tag?tagname=spam