Logically, no one who is going to ignore someone will do this, but:
Imagine that I have a user being "followed" by the bot. And later I "ignore" the user on the forum, what will the bot do? Or I "ignore" a user on the forum, and then it comes to the bot and I request to "follow" that user, how does the bot react?
The only "ignoring" that matters is the bot's in-house ignore list.