Yes, as in "same anon who made the post I'm replying to." It's not used frequently, usually just for typo corrections and such. It's basically "Edit:"

AYRT = "anon you replied to"
DA = "different anon" (used if you're serious about clarifying that you are NOT ayrt, usually to either +1 the other anon's point in a heated debate or chime in to offer a different perspective)
NA = "new anon" coming into the thread for the first time. Almost synonymous with DA, so this one is rarely used.