'at' makes sense, in fact it has been a great pick for the email protocol.
The problem is actually the "multiple uses" with completely different goals. Try to explain to a casual user that your are giving him an email that does not work as an email, paired with a 65 chars password that cannot change... panic.
Should a Nostr identifier suffers this bootstrap weight? Or is better to start telling a new story with new rules?
I suppose that for this reason someone (maybe Alby?) started to propose to prefix the LN addresses with the emoji ⚡, to mitigate the problem and make them recognizable, by humans and programmatically.