It's only on a forced ignore which the moderators have stepped in to not only force two members to place each other on ignore but to prohibit the members from commenting under each other or to thank/hug each other or on the same post as another member. This is usually an extreme measure when two members have violated the rules and guidelines repeatedly towards each other, and breaking the forced ignore can result in suspension. The moderators would have made it clear to you of these rules. Sometimes mods will say "If you do not like this member, put them on your ignore list" It's not a hard limit, but a suggestion, and it does not mean you are on a forced ignore.

However, let's say you ignored me on your own terms aka without the moderator's stepping in. I wouldn't be able to comment on your threads, but it's perfectly acceptable to post on another member's posts and thank/hug other member's when you do. I do find it odd, however, that you can still post on the threads of someone you ignored, yet they cannot do the same to you because they are on your list. I would prefer some notification that says "You cannot reply to this member because they are on your ignore list." It's typically only when moderator's have stepped in and set hard limits that can result in suspension if you comment under an forced ignore's post and such.