Do you think that Blurtit should display an 'up-vote' and when you 'thank' a writer in your feed? Or is this not necessary?
I agree. It should be up to the user. Whether they rate you up for answering or a great answer, that is up to the user.
I don't think Blurtit needs to show 'up-votes' and 'thanks', as if you're following a lot of people, and you can see everything they've up-voted or thanked, then your feed is going to get clogged up very quickly.
I've had this happen a few times myself when I've been working in a certain category. I'll find that my feed is filled up with what I've up-voted and thanked, which is often several answers to the same question, or multiple questions on the same subject.
I then feel sorry for everyone who follows me, as I know they're likely to end up with a feed full (for example) of crustacean-related 'thanks' and 'up-votes'!
Let The User Decide
I think the best thing would be to let each individual user decide whether or not they want 'thanks' and 'up-votes' appearing in their feed.
If feeds were customisable (perhaps under 'account settings' or even in the form of a tick-box or two on the feed page itself), then everyone would be happy - you could have both 'thanks' and 'up-votes' hidden, or only one hidden, or both showing up.