When removing a defunct user account, the safe move is to delete and merge; alternately, you can just obfuscate the account's email and password.
The slide deck from my WordCamp Maine 2016 talk on WordPress security. Note: Only fools heed the advice of context-less slides found on the Internet.
There's a difference between 'haggling' and 'arguing' over price. Haggling is fine, and here's how to spot it.