My point is that I shouldn't be expected to use a search engine to understand terms of a post in a generically themed community, it costs nothing for the user to put the definition. How common the term is IS something to consider when deciding to put the definition or not. Considering that the most up voted and commented comment is about the term not being recognised, I'd say that my point stands.

MIL should have the same thing unless it's being used in a thematic community like relationship advice. It's common practice for a document that has shortened terms to have parenthesis with the full definition the first time they are used, and in a post thstbwould be the title or the body of the post.