It sounds like you still might be a little too tuned in to your ex? I can't imagine that you meet that many people you haven't seen for six months, that often? If someone I am only acquainted with (haven't seen or talked to in six months; they don't know what I've been up to and I don't know what they have been up to) were to ask me about an ex, I would merely state that we were no longer together and change the subject to them and their affairs.

I'm sure it happened a lot in the first couple months, but now? The number of people who know you and don't know you've broken up has to be kind of small? If you have people who are asking "again", who know you are broken up and are curious about your personal business with no reason to be, then I'd be pretty rude with comments like TheByzantine suggests.

But I don't spend a lot of emotional effort on acquaintances I haven't communicated with in six months that ask random questions, probably the only thing they may remember about me? That's okay with me, for them to ask whatever they remember; if they don't ask about me, first, how I'm doing instead of how my relationship is doing, that is very telling as to why they're acquaintances and not friends