I just find it very odd, the seeming beginning of a Lemmy culture of "you would downvote me? EXPLAIN YOURSELF SIR"

No, I should not need to explain myself, a downvote shouldn't carry that much weight, it's not that big of a deal. Less than a middle-finger or even a thumbs down. At most a disagreeing shake of the head in conversation.

Further, the reasons can be their own, maybe someone wants to downvote everyone with a username starting with "h" just for a fun gimmick.