At one level, it's absolutely correct that hurting those you care about is the really painful part about getting close to people. The comment goes on to claim that it is the mismatched expectations that cause the pain. I'll certainly agree that the pain I am discussing tends to happen when there are mismatched expectations. I also agree that is incredibly difficult. However I don't think that is specific to poly: it is a basic consequence of relationships and getting close to people that when you are unable to give someone you care about something that is important to them, you are both hurt. I don't think I'm new to that though; I think I've been dealing with that pain most of my life. While it is not easy, it is not surprising.
The new pain here is the realization that even when there is overlap in expectations and desires, the resource management (mostly time) may make it impossible to actually realize these shared desires. I simply do not have the resources to make commitments to all those who I'd like to make commitments to. Now you can look at this as me not actually desiring to make the commitments after I've looked at what resources I have to offer and thus reducing to the problem of hurting those I care about. I don't see it that way and it certainly doesn't feel that way. I find it qualitatively more difficult to decline something that I want than to decline something that just isn't right for me. Now the comment definitely has a point: the aggregate effect is what makes this all difficult. However, I do think that resource management is a very important focus for thinking about the situation.
I think this also gets at Leaf's question. I was not actually contemplating changing anything. I think the possible changes would be to avoid commitment as I discussed in the first article; to make commitments as they become possible without thinking about the future and my long-term goals; something close to monogamy; or to avoid getting close to people unless I somehow already knew that our expectations and resource availability would line up. Acknowledging that life will be painful and that pain is part of the price you pay for the wonderful parts of closeness seems like a far healthier option.