When we ban an account, we don't use shadowbanning it unless it is relatively new and shows signs of spamming or trolling, or being related to past abuses [1]. When an account has an established history, we say that we're banning it and why [2].
We rate limit accounts when they post too many low-quality comments too quickly and/or get involved in flamewars [3]. We're happy to take the rate limit off (and often do) when people give us reason to believe that they'll use the site as intended in the future. Emailing hn@ycombinator.com is the best way to do that.
Creating accounts to get around these restrictions is obviously a repetition of the original abuse and will get your main account banned as well if you keep doing it, so please don't do that.
[1] https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
[2] https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
[3] https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...