Yes, mate, I have a kind of idea about this, as I was exploring this forum and saw that there was another signature campaign of the mixer that was managed by another forum manager, and that was the campaign of the Ethereum mixer, but as we both agree at the same point, it is very easy to get scammed, as many of these services are just made with the intention of doing scams with users. So, if these kinds of reputed services like "MixTum" start to provide altcoin mixing services as well, it will be a bonus point to the users to use the trusted sites/projects to mix their alt amounts.
Unfortunately, scammers take advantage of users' inattentiveness. I remember last year, there was a case when a user claimed that one of the mixers advertised on this forum allegedly scammed him for 10 BTC. Most likely, that user just got victimized by another phishing site, of which there seem to be a lot in search engines.
Honestly, I may be wrong, but it seems to me that the advertising campaigns of Mixtum and other mixers on this forum are useful not only in terms of promoting their brand but also for pushing scammers out of search engine results. I guess this might be because forum pages are well-indexed by search engines.
Yeah, you are absolutely right, I can tell you for sure that there have been a lot of times when I want to visit a casino (for example) which I don't know the exact url to type into my browser, instead of searching that casino on Google, I simply will enter the forum and find it on a user's signature ad and enter the casino from there, this is to avoid getting on the wrong copy of the site I intended visiting.
So, signature ads isn't just about getting more people to know about the service being advertised, it also provides people with immediate available and trusted link to the service, reducing the chances of a prospective customer ending up on an impersonating site.
And about the user who lost 10 btc to a mixer, yeah, it was Unijoin actually,, the user visited a fake Unijoin website and lost 10 bitcoin to scammer who created the fake site - this is if his story was real anyway.