I have not see any logic at all.
I'll show you.
What is "Burst posting" 
This is:
(Note: Check the timestamps)
Is it forbidden to write many posts here?
Not forbidden by the rules, but it is frowned upon.
What is "low quality posts"
This is:
If other messages are "low quality" why there are not deleted then?
It is not necessary for a mod to delete all the messages of a user if they are about to ban him. So, only because the mod who banned you did not delete all your messages it doesn't mean that they are not of low quality.