gosh it isn't "narcissist" to not "check the latest couple dozen posts". I guess you are a person who sits all day and all night at a computer ya?
Especially with the weird sorting on the fediverse you could miss it even if you read 25 posts. But do I read >24 posts every time I post 1? No.
If the URL is identical the software should let the user know when posting. It happened to me on reddit before. it would let you post it but you had to confirm. Usually I'd just kill it at that point.