User 3 in this article was banned for "spam" which as far as I am aware is not illegal. Gizmodo received a response from Gab saying "spam is not free speech."

https://gizmodo.com/even-the-freest-free-speech-site-still-b...

Also, HN user encryptluks2 says he was banned "for making a post asking how are all the domestic terrorists Trump supporters doing after the capitol riot." They may be able to give you the info to verify.

https://news.ycombinator.com/item?id=26339259

Also, any form of sexual content is banned on gab which is also generally protected free speech. I'm not aware of anyone having been banned for it but I'm sure they are out there, and if not it is easy enough to test.