If you have not posted or voted, you should see a "delete" option on your profile page (next to "edit"). Otherwise, you can request deletion of your account by following the instructions here. (Additional info on MSO.)


The on-site search doesn't support searching for posts from deleted users, but you can use this SEDE query to find all posts from any user name. Note that that query uses name, not user number, so you have to formulate the parameter as "user####" rather than "####" and (I assume; didn't test) if you search for a name used by more than one user, you'd get ...


While I can't say for certain, I'm pretty sure these are user accounts that have been deleted.

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