Std english rules would indicate "vaper" is the person vaping.
Plus, "Vapor" already had a definition.
The "er" indicates something that does the action....boxer, gunner, walker, runner, lawyer, etc..
And before some wiseguy chimes in, "doctor" and "mediator" don't count because there's no such words as "doct" and "mediate" already ends in "e". If a word ends with an e, it's changed to an "o", like "educator" or "terminator".
Words like "traitor" and "sailor" are just weird exceptions that English is known for
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