I personally am not much of a blogger, so my own proclivities as a blog writer ('fuck no I don't allow comments on any blog for which I am responsible for picking up the dogshit and spam') aren't too relevant. But many of the blogs I find most valuable do not feature comments, or if they do, they are 99.9% what you'd expect: utterly worthless, time-wasting digital turds.
I think the whole comment thing is misguided. If you really had something worthwhile to say, why on earth would you entrust that to whatever crap-ass 'blogging platform' that blogger in question happened to be using at the moment?
Say it somewhere that you control, and link it. That's how the web works.
Of course, I have seen worthwhile comments (especially on blogs where the author takes the time/effort to aggressively police them). But that's far and away the exception, and not the rule.