I agree! We need to stop this insane spamming by those two users. They don't have a single idea how bad the situation has become after they started personally targeting the community and those wearing the signature. I am in support of creating a flag against both users.
You cannot stop a user from spamming, all you can do is report a spammers post to the moderator, though i don't think they are going to delete this members posts. My suggestion is to completely ignore this member and with time they will stop derailing this topic. I don't think creating a flag is appropriate for this, a trust feedback may be a better option, just to tell or warn other users about this member.
Should this have been a sled moderated thread where such users gets there off topic posts deleted quite often, I think the user would be mindful of what they post in such thread as, it’s most likely going to be deleted and that would mean a waste of effort. No one likes their efforts to be wasted. Same effect would be the case when the posts are being deleted by a moderator and should such user continue with such posting style, a temp ban as stipulated in the rules would apply. These are supposed to work effectively as well as, neutral tags to bring the users attention to their posts. Creating a flag, not really a solution the way I see it.