Well, I tend not to add anything that doesn't aid the user. So, if a button might help give some context, I might add it. But if there's many buttons on the page, then I might not use icons or it may overwhelm the overall perception of the page. 

In the example above, it might help to add an icon to the middle button just to make it stand out a tiny bit more. Might look better too. 

 Yeah, exactly what got me to think that, clarity vs intuitiveness vs noise and then whether it's a matter of taste or a design standard thing

Firstly though, hmm maybe I'd add icons... but maybe that's noisy and less satisfactory 

sorry for yapping so much, just curious 

 I think you nailed it. Just need to play around with intent and see what works. Ultimately, users will also inform you of something needs tweaked.