I usually use Chrome for "everything", but lately I have wanted to use Firefox for more stuff, because I "politically" might not be aligned with Google.
So I fired up Firefox, browsed around and was quite happy with the experience, and then logged into OLD.reddit.com. (I can't stand the new UI).
After some "messing around", my account was suspended, with this message:
Evading your ban in r/... from 2023-09-29 on a connected account. Moderators get to decide who can participate in their subreddits. Using alternate account(s) to circumvent a subreddit ban makes it more difficult for moderators to effectively run their communities and is a violation of Reddit's rules.
Yes, I was banned from a subreddit. And that was by bad, and is totally OK. Three weeks later I was banned for using a different browser, with no reason given.
I am banned in 2 subreddits (run by the same group of mods). I was banned for breaking the rules. Fair enough. Like many people I have more than one reddit account and while logged into an alt made a comment on the sub I was banned from.
Different account name, same browser, probably the same IP and it was a perfectly innocuous comment. Nothing bad, nothing rule breaking. I assume the mods joined the dots, told the reddit admins and I was suspended from reddit for I think 2 days. Maybe 5. Maybe 7. I really cannot remember.
I also use Firefox, Firefox Dev, Edge, Safari and Brave to access reddit but FF is my main and old.reddit.com is always on.
What I suggest you did was to login with a different account and then comment in the sub(s) you are banned from. They suspended you which is fine - they do make this very clear. They got me, they got you.
It has nothing to do with browsers.