This whole subthread spawned from one sentence where I asserted that I found it valuable when my friends would tell me if they thought my songs sounded too much like something else (and that they expected the same from me), as an illustration that there are contexts in which asking about originality is something that would be reasonable for a friend to do. Nothing you've said so far seems intended to refute any of that.

I stand by the notion that the definition of "cover" and "original" song are not especially ambiguous, even though music appreciation is subjective and there are edge cases where reasonable people may disagree about whether two songs are "too similar" to be considered distinct songs.