Testing people well, never works.....

You said you don't care so much about the Comicon as not being directly invited. Do you actually have an interest in the things that are present at the Comicon? (I'm unclear on if it's of any interest to you beyond doing something with people you know). If you don't really have an interest in the Comicon things, then it would make sense to not invite you to it.

To me, hearing someone going "Sure, you're invited!" is an invitation and even a bit of assumption that you would be attending. I wouldn't cut that person out when they did confirm that you were invited.

Of course, if being relatively excluded from the planning-process of things all the time is a pattern, then I'd be getting sick and tired of it too. But like others have said - you should try to be much more explicit with them instead of giving them a doomed test. Try asking "Why do you never invite me to things?" as opposed to telling them how you feel. Asking them a direct question requires an answer which could then lead into a discussion - but it wouldn't allow them to dance around the topic.