But when there are many quotes the last user can not add great thing! To solve this problem is he can add an option to limit the number of quotes per comment?
Or even better add a boundary length of each quote? (eg 400 chars per quote)
Such a thing would need a lot of code and template changes - we'll consider it for a future release.
Couldn't your users simply press Reply instead? You could remove the Direct Quote button and only have Reply if they are too obtrusive - with Nested Comments enabled, the need for Quoting everyone all the time doesn't become necessary. And you could remove the Quote BBCode button too if you really wanted.
Apart from that, yeah... lots of work would be needed to add this feature.
It's really a major worry to see your site no longer works because a very long comment!
This is breaking your site?