It's similar to a like button.

It serves no real purpose in eBay except for letting ones peers know that you think the post in community is good.

I also use it so others know I have seen and read their post, especially if it's a reply to my post.

We also have some comps running in community spirit and use kudos to vote for posts you think are good.

If you want to have a look at CS then select groups then scroll to Community Spirit.

A place to post news, chat, comps, bit of fun in general.