In your account page (https://news.ycombinator.com/user?id=bobwaycott) you have the "showdead" option, which lets you see dead comments. You can then look a user's comment history by clicking on their nickname and on "comments". Shadowbanned users are those for whom all comments are automatically dead.

I had to create a new account since I lost password of my last one, but I had noticed in my last account that my submissions (not comments, but link submissions or Ask HN submission) would be shadowbanned right from the start? And this was on a fresh account that I had. Does HN shadowban by IP?

Email the mods via the Contact link in the footer and they can definitively determine why the account is shadow banned.

Ah, gotcha. Thanks!