The process would be automatic. I don't believe it to add load on moderators, because if a post is worthy to be deleted, the user having posted it also is 99% likely to be a spammer. There may be exceptions, for example people posting drunk one day. But as it's not a ban, only a signature removal, and with 10 merits you can revert it, it's not an overly harsh punishment. People would eventually "get it" that they can't post shit until they are a Member

I really hope it works. A problem I see here is that one single merit is also pretty easy to buy, or get exchanged for a "lesser bad post". In my proposal, instead, you always live in danger if you do shitposting, until you get 10 merits.
But the real reason I don't really like the requirement is the effect it could have on honest new users. Not everyone likes to write tutorials and so on. Until they know that they need a merit to rank up, they could complain not being welcome. It's a bit anti-natural for a forum to require a "merit" to rank up, and so it could be regarded as an entry barrier.

These farmers would all lose their right to wear signatures very soon if my proposal became implemented, often before they could get paid out. The effect should be the same one than with the current rule: Nobody could get money for nothing (with the exception of off-forum campaigns like at Twitter, but these should not bother us here).

That could happen, but they would have to shitpost without being discovered, until they become a Member, then they could do what they want (but would risk a ban if they break the rules several times).

I think you misunderstood. We were talking about the risk to get the signature removed if a whole thread was thrashed. If the software, for a signature removal, requires that it additionally must have been reported, then that cannot happen.