Ask only if you are familiar with the context of the question
Stack Exchange is a site "for experts". While our definition of experts is a little broader than usual, it doesn't change that fact and terms are part of that expertise. For me, this is a similar issue to the one found here: Should I ask a poster to quote the rules he or she is confused about? - the question is supposed to be read by people that are familiar with the context of that question, i.e., a question about Pathfinder is supposed to be read(able) by people familiar with Pathfinder's rules, and a question about AL should usually be read(able) by people familiar with AL, including their terms. Another way of seeing this is: We don't ask people to spell out RPG, D&D and other common terms.
That doesn't mean we should be a closed group that speaks an underground language that nobody else understands, but if someone is confused with usual RPG terminology, we do have the terminology tag, which is exactly for "I don't know what this means, can I haz explanation?"
On the other hand, if you are familiar with the context and it is still unclear on what that term means, then you should ask for clarification.
Edit only if you are really familiar with the context
As SSD mentioned in his comment1, some terms have more meaning as the acronym than as the spelled out version. Edits for clarification should only be made if you are completely sure it is not going to change the meaning of the question in a significant way. Also, only edit if the term isn't, somehow, part of the problem which leads to the question - obvious examples are the terminology questions asking what the term means.
“HC” means “hardcover” — ironically it is less meaningful spelled out, because only in jargon-y “HC” form does it carry any meaning relevant to AL