<quote user="alphacentauri"> A year is a long time to not even use the browser add-on.[/quote]
There is a difference between an inactive user account and having the add-on installed and active in a browser.
If User_X has WOT installed, creates a forum account posts 10 replies on the forum, rates and comments 50 domains in 2010, then in 2011 they decide to log out and not allow the add-on to log them in automatically. So they still have WOT installed and may still be rating sites anonymously, but the old account is now inactive
Since this is 2013, the registered account has been "dead" for 2 years Assuming the methods proposed in the OP were in effect, the scorecard comments would have been deleted in 2012 (1 year inactive) and the ratings would be deleted this year (2 years inactive) however the user name remains, the forum posts remain.
User_Z forgets their original account:user name which was using a Hotmail email account created back in 2008
The user creates a new registered account using GMX email address in 2013
Any scorecard comments and ratings made by that 5 year old inactive account should be flushed.
Yet another scenario
creates a new account every 3 days, rating and commenting on 20 domains to attempt to earn reliability.
As time moves forward, this person has created approximately 487 user accounts in the past 4 years.
If the OP methods proposed were in effect, 1/2 of those accounts would be flushed though the user names remain.
Last but not least
Let's not forget about [url=http://en.wikipedia.org/wiki/Sockpuppet_%28Internet%29 t=_self]sock-puppet accounts[/url]
I would like there to be an RSS feed for comments to my board
The PM system is set to deliver messages as private by default.
An RSS feed is public
If an RSS feed were created, it would only display posts which were manually ticked non-private