Hello and welcome @whywhy 
As Discourse Trust Levels are customisable, different sites can have different abilities and thresholds for each. I think our defaults are relatively easy to understand, but not every site will stick to those defaults and will tailor them to suit their own community values.
You’ve obviously had a less than ideal experience at some point, but I don’t think it’s fair to say that the software (or Discourse communities in general) operates with any intentional malice. We’re here to promote civilised discourse, so that kind of ethos would not be in keeping with that.