Django Model Field for Abstract Base Class

I've searched around stack overflow for an answer to this (probably simple) question, but most of the solutions I see seem overly complicated and hard to understand.

I have a model "Post" which is an abstract base class. Models "Announcement" and "Event" inherit from Post.

Right now I'm keeping related lists of Events and Announcements in other models. For instance, I have "removed_events" and "removed_announcements" fields in another model.

However, in my project, "removed_events" and "removed_announcements" are treated exactly the same way. There is no need to disambiguate between a "removed event" and a "removed announcement." In other words, a field keeping track of "removed_posts" would be sufficient.

I don't know how to (or perhaps can't) create a field "removed_posts," since Post is abstract. However, right now I feel like I'm repeating myself in the code (and having to do a lot of clutter-some checks to figure out whether the post I'm looking at is an event or an announcement and add it to the appropriate removed field).

What is the best option here? I could make Posts non-abstract, but Post objects themselves should never be created, and I don't think I can enforce this on a non-abstract object.

My understanding of databases is weak, but I'm under the impression that making Post non-abstract would complicate the database due to joins. Is this a big deal?

Finally, there are other fields in other models where I'd like to condense things that amount to an event_list and an announcement_list into a post_list, but those fields do need to be disambiguated. I could filter the post_list based on post type, but the call to filter() would be slower than being able to directly access the event and announcement lists separately, wouldn't it? Any suggestions here?

Thanks a ton for reading through this.