I hate it when…

Someone sends you an official message with an ambiguous passage, you write back for clarification, and their response begins: “As I already mentioned…” (i.e., “If you had read more carefully, you would not be wasting my time with this needless follow-up.”)

In the first place, it is usually the case that they didn’t “already mention” what you are asking about.

In the second place, people sometimes overlook things when reading, and it seems a lot simpler just to answer their question than to let them know that you already told them once.