Meta-truth:
Many shady techniques are used by otherwise innocent people, often only one or two techniques at a time, because they imitate what they think works by the "biggies." So for example, some new or otherwise legit authors see subtitle stuffing and think it's okay because so many "successful" people are doing it.
But really shady operators and scammers use ALL the questionable and outright prohibited techniques they can, to get an edge, unless they are actively slapped down.
So, the more of these techniques you see someone using, the more likely they are a self-aware scammer or shady operator, rather than someone who is simply clueless and trying stuff out that they think is okay.
It's the "where there's smoke, there's probably fire" principle. Occasionally it's just mist or dry ice vapor or fog or steam, or a smoke generator, but more often than not, it really is a fire. Or it will become one.