Questions like this must be emailed to dang hn@ycombinator.com if you are asking about details specific to your account, submissions or comments. I do not see dead or flagged comments associated with this account. I assume you are asking about a different account?

If your account is new i.e. Green there are triggers that can cause submissions to be auto-dead. If you open a different browser or private tab that is not logged in you can see if your comment or submission is shown to the public. People with show-dead enabled would still see your comments and submissions.

I see a non-dead comment from you, so it doesn't look like you're shadow banned. I do see that you posted the same comment three times across three accounts on a thread, so that's definitely not behavior that is encouraged here. I'm guessing your original comment got flagged (maybe by humans, maybe not - no clue) and you attempted to re-post from other accounts which likely marked your posts as spam.

As mentioned in the sibling comment, reaching out to the moderator is the best way to figure it out.

Update: the thread seems to have fallen off the Ask HN page very quickly so there does seem to be some penalty applied.