Posts about Macintosh and Windows also have different colour background.
The "heart" icon is on posts that are my personal favourites, posts that took a lot of work, or most popular in the feedback I've received. It's just a way of me showing the posts new visitors might want to read first.
I'm not mad keen on the pin symbol, I'd prefer it to be mono, but I couldn't find an alternative that looked good.
Thanks for reading