I do not know what are the merits of downvoting except to discourage newcomers and appaling from continuation of discussion, but, IMO, it does not have sense without filtering users feature(s).
Some users are continuously chasing my posts just to insert off-topic comments, mostly the same.
How would I block some of the user's postings cluttering my view?
I'd like to see in SF the feature permitting to prohibit certain users from accessing my posts (viewing, editing, commenting, answering).