It's an unfortunate consequence of the reddit interface that you can't join any conversational thread in which she is the last person to post, without your comment having to be a reply to her that shows up in her messages... even if you aren't even trying to interact with her. I'm worried about the precedence of non-moderators on LW essentially having the power to ban people they've had conflict with out of interesting discussions. [Edit: realized that Alicorn is currently a moderator. My point was to discuss the potential problems from User A requiring that User B never reply to them on a Reddit-style interface, and how it can effectively become an unofficial thread-ban, not just a reply-ban, even when mod powers are not used.]

The ideal solution in my mind is if it's OK by Alicorn for you to respond to anything that she posts (at least, when you don't ask for a reply), and she has no obligation to reply to you. (Of course, you must limit these replies to be abstract, and resist any urge to make them personal or snide.) Given your past interactions with Alicorn, I don't think it's a good idea for you to reply to her and attempt any discussions, but it seems a bit steep if you can't reply to comments by her, even when you aren't trying to have a discussion with her, because that potentially locks you out of threads that others are reading.

Failing that, the next best solution is probably to just take the high road and not respond directly to any comment by her, due to the conflict and status hits incurred to both you (and her) in the eyes of various observers every time this comes up, particularly when you make "terrorism" comments. If she posts something interesting, often other people will reply to it, and you can reply to them.

If you must respond to a comment by her simply out of interest in the topic, I suggest that you keep it impersonal and neutral, and she can simply ignore it.

As you know, I don't think your punishment is proportional to what you've actually done. But sometimes people are going to be unfair to you, and often the best solution is to just move on and live your life.