Not sure what your rationale is with this approach.
Me neither! And I'm wondering where did you get the idea for the need to have it separated and what do you think to gain with this needless complication?
The core can't always provide for this user deletion, because every module has its own database tables where info posted by the user is stored. Comments are a general function and there it could.
I will think about some PHP code to clean up comments per user.
If you want it automated, you should explain what is the 'raw' source (database, calc sheet, ...).
Some modules can do kind of listings. It depends on what and how to list. Examples are xRoster, Formulize, catads, xdirectory, shopping modules as Oledrion, ...