That thread should be reported to the moderators for spamming.
I've just reported it as you said. Now it's up to the moderators to decide.
If you really want to clean it up, I suggest you report such posts to the moderator. After some time, they themselves will give up this strategy.
Also, tagging such accounts is not wrong, so I encourage you to do it. Just make sure you make valid references (probably the best in this thread) in case the OP decides to delete his topic.
I already tagged OP (neutral) but I am not so sure about the other alt or related accounts. I think this alone is not worth it. As they have had no activity since their inception, I think they will be seen at the next move they make.