Thumbs up icon on post?

[Craikeybaby]

I've been on PH for a while now, but this is the first time I have noticed a thumbs up like this on a post
(link: https://www.pistonheads.com/gassing/topic.asp?h=0&...

It doesn't have a link, or a tooltip, there's not even a descriptive class name when inspecting the code - all of the other top of post icons have a div with a descriptive class name. So I was just wondering what it is?

[silentbrown]

[Craikeybaby]

I must have seen that over 11,000 times still not noticed being used much though...

[Master Bean]