Note how out of the 30+ shills labelled in past month that none have complained about it 
I think that this system with badges and a mark on the forum is perhaps a little more complicated. Too many different labels, and it's a little harder to find more details about them.
The bad badges are all referenced
here, linked at bottom of the
main topic about it, even referenced and linked in the second highlighted topic in the top right corner of the forum "Everything about Ranks and Rank". If anyone wanted to find the meaning of these badges they would only need to search in beginners section for the answer, or otherwise ask the question for the hundredth time. The reason there is a diversity of badges is because we don't just label all users as "misbehaving" or otherwise, but specify more precisely how they are misbehaving, or have broken the forum rules etc.
Granted there are some membership groups without badges (local mods, ex mods, under review, etc), or otherwise groups without self-explanatory descriptions like zoom1, but that's a different story. Why users are in zoom1 and not duplicate profile membership group I don't understand, that's for admin to answer, or ideally just resolve with another badge.
Many users, even if they are not registered just to shill, do not even notice such marks, if they do see it, it is not so obvious whether it is a positive or negative mark.
The labels/badges are not for the benefit of the users themselves, this is a common misconception of the purpose of these bad badges. This is what the warnings are for that specify exactly why they have been warned/punished. The shill warning template specifically references
this post, as well as forum rules, how to rank up without penalties, etc. The badges are solely for the benefit of everyone else, so users can be aware that a shill may well be shilling, or otherwise bounty managers when accepting new participants to campaigns for example.
I just gave him another 20% warning, it is the second warning that this user has accumulated and he also has negative Karma. I'll keep an eye on upcoming posts to see if the user notices anything or is looking for the third warning.
Thanks for your help.
+2.
I have one question - does this mean that the first warning was not visible in his profile (because I did not see anything of that type yesterday), while today I can clearly see that he has been added to a new group and that he has a warning?
Warnings on profiles are not visible to non-mods, not even the user themselves. You are probably conflating warning level and warnings here. The
warning level was visible on profile as it was +20%, (
which is over 10%), so they are additionally added to the watchlist to keep an eye on. The membership groups are not warning levels and is a different system, they are simply used in combination. For example when users are added to shill group, or receive a strike etc, then they are additionally sent a warning. Warnings can otherwise be sent with no warning level, or without even sending a warning to the user.
Personally, I would give a warning in the form of a temporary ban of 7 days with the message that any similar behavior will result in a permanent ban. Everyone deserves a second chance, but it should be done in a clear and efficient way.
I already posted about this before, but to summarise again first offence is a warning, second offence is being added to shill group + 1 strike, third offence they are added to misbehaving group with a 2nd strike. Misbehaving group is a moderated group, meaning all posts have to be approved by mods to be seen, so it becomes impossible to shill (aside from mod errors). This is actually a lot more effective than a ban as shills who attempt to continue to shill will not have their posts approved, and otherwise are more likely to continue trying than immediately creating a new account to carry on. They can also be added to 3 strikes group which requires admin approval (from admin or president), so overall slows down the effect of shill creating new accounts (though usually after a week or two they work it out).
For a long-time we've had the ability to temporarily mute users, but is rarely necessarily or beneficial. This is only for cases where a user is repeatedly breaking the forum rules daily, or multiple times per day. Then after 3x 20% warnings the user will be muted, or otherwise with 5x warnings they will be muted for approximately a week with 100% warning level. It's otherwise not a very effective solution, as most of the time these users will simply return to bad behaviour after no longer being muted, hence 3 strike system is preferred, as having posts require approval from mods/admin, by being added to misbehaving or 3 strikes, is a much better solution long-term. We don't want to delay shills reaching misbehaving group if that's their intended destination, it is better to let them carry on shilling so they can be added there sooner rather than later. A temporarily ban would only delay this process for most, and thus become a waste of time.
I imagine that all sounds relatively confusing, which is exactly why we have very detailed moderator guidelines and only promote mods to global mods who have the experience of when to use membership groups for different reasons. As it's certainly not straightforward, and usually takes a year or two to fully understand if I'm honest, or longer for others.