Deleting an account puts the IP, email address and URLs they may have posted into the corresponding Screened Logs.
AFAIK:
pros - the IPs and email addresses in Screened are used to help stop new accounts from registering using the same IP or email address
cons - the “paper trail” of evidence is gone
The IPs can “roll up” to block IPs within ranges and email addresses have a levenshtein setting.