The reason it took me so long to add those buttons is that I didn't think anyone would need them. My guess is that anyone who uses those reading services would already have the shortcuts added to their bookmark bar on the browser window. (That's where I have mine.) But I added them today just to see of anyone found them useful.
While I was at it, I also replaced the recent comments widget. It's been broken for a while now, and I've been fiddling with the code and trying to fix it. I threw in the towel today. It took me maybe 5 minutes to find a dozen alternatives, pick one, and install it. trying to fix the broken one was clearly a waste of effort.
P.S. If you look at the picture you might notice the new subscribe buttons on the top row. Those have actually been there for a couple months now.