I feel this would be a very poor design decision.
Apple's HIG specifically calls out "Do not use a push button as a label."
The OS X button style is reserved for clickable UI elements and if we used them on items that are not Cocoa controls and instead web links - I feel it would undermine the clarity of purpose that OS X provides under it's Human Interface Guidelines. And that's the best spin on it for people browsing from OS X browsers.
It gets worse if you are browsing from an iOS device where the button treatment uses another idiom. Likewise Ubuntu, Windows, Android, etc….
I get the wish to have pretty things - but I'd personally rather a "design is how it works" interpretation here over a "design is how it looks" design.
Thankfully, the site has redesigned the tag buttons and they look very nice on both retina and non-retina screens of all OS (again perhaps only in my opinion).