https://news.ycombinator.com/replies?id=<CommentUserID>&by=<ReplyUserID>
E.g., dang's replies to bigbacaloa:<https://news.ycombinator.com/replies?id=bigbacaloa&by=dang>
That (presently) turns up two admonishments dating back 11 months and two years: <>>37423572 > and <>>33132910 >.
The first of those (11 months ago) is where the account was banned.
If you have specific questions on accounts, users, sites, comments, posts, etc., which you feel are improperly flagged, killed, or banned, you can always email the mods at hn@ycombinator.com. I do this frequently, usually with suggestions (e.g., title or URL changes), sometimes with questions (earlier today a site which showed up dead, turns out it's a hard paywall, which I eventually tracked down dang's comment on, though not in an easily-searchable way).