Here’s what I think happened. It’s just an opinion.
First off, if all or even a double-digit percentage of bans were frivolous we’d hear more about them. Instead we usually see one post per month and the OP usually weaves a tale with lots of places that feel embellished. If they manage to push the staff to reveal more details it’s 99% embarrassing for OP.
Your story is not sending all of those vibes, but your attitude is matching the 50% probability flag: you’re really upset about a minor thing that most people don’t seem to stumble into, and you’re convinced that there is a larger conspiracy targeting many players based on one thing that has happened to you.
The first ban I find marginally understandable because even if it was a joke it’s spammy AF and I’d be happy to see someone banned for typing an entire song into global.
The second ban you had confirmed as a mistake by staff so doesn’t count.
The third ban you admitted you strongly deserved, and you know it paints you so badly you decided not to elucidate. I’m a cynic and that makes me believe you did something so petty and stupid you think if you detailed it in this thread nobody would take you seriously.
Before we move to the fourth, here’s my hypothesis: this ban was so popular with support it made a name for you as a troublemaker and they noted your account as having multiple bans and one very negative outburst. This is a bad position to be in for you. Once you have a reputation as a troublemaker it’s easier to get into trouble. Nice people have a little bit of social credit. It’s not fair, but it’s how human nature works and part of socializing is learning these rules.
The fourth ban, tied to Salty’s choice to mention temporal separation between offense and ban, leads me to believe you said something homophobic some time within the recent past, someone reported it, and support just got around to that particular report. I find this especially likely because your third ban is so mysteriously bad you can’t tell us what you did, even though you claim you grew past it. Personally I think you’re still in the “denial” phase.
As corroborating evidence: people in this thread I trust are detailing that you’re also loudly complaining and arguing about this in global. This makes me believe even more you’re not super clear on the connection between “I do things that upset people in global” and “I get banned”.
Were I in your shoes, I’d disappear from global for a while. People have short memories. I’d use that time to reflect on what I said to people and decide if it was really worth it. It’s usually not.
To answer your initial question: no, it’s not the general consensus that any proportion of bans are unjust. We do know sometimes mistakes are made, but we don’t see many of them because they often don’t involve people who make a page-long post making accusations of widespread injustice when it happens.