So I've just noticed there are heart frames round some people's questions/stories but not others and randomly

Plus they weren't on here yesterday, on valentines day when I was on...
Now I'm wondering if other people can see them. Or if it's just showing up for some, like the red/pink title bar some people had? Or if they decided to implement it after @soosie 's suggestion? I know we are all in different time zones but I think I was on in morning and did pop on a couple of times later in the day yesterday too.