For what it's worth I didn't have your tweets in mind when I wrote this, but it's possible I saw them a couple weeks ago when the Discourse was happening.

Thanks for linking to the post! It satisfies most of my complaint about people not providing reasoning.

I still have some objections to it, but now I'm arguing for "there are no good reasons for certain actions to be supererogatory," which is a layer down from "I wish people would try to give reasons."

1. The post mostly gives a description of people's attitudes toward different actions, but not so much a justification for those attitudes. (Reminds me of this paper on moral attitudes toward tradeoffs.) I agree that no one thinks it's blameworthy to stop short of donating your last dollar.
2. To the extent the post make a normative case, I also agree that morality has to account for the pragmatic considerations you name (uncertainty, coordination, cognitive limitations, etc), rather than naively trying to fashion the world after your favored axiology. But I think the post makes the right response: you can just factor in those considerations, and the resulting morality might still allow offsets / be demanding. "People are only going to do a certain amount and then get tired" but maybe we're obligated to be tired a lot, etc.
   1. Side note: I think it's interesting that your argument against demandingness came out of an argument against offsets because another argument against offsets is related to demandingness: whenever you're considering an offset, one option in your choice set is to buy the offset but not do the bad thing, so you should always do that. 

On obligatory: maybe using this word was a mistake, I used it because it's what everyone uses. If it means "blameworthy not to do," then I don't have a position. Finding the optimal schedule of blame and praise for acts of varying levels of demandingess is an empirical problem.

I meant obligatory in the sense that moral reasoning typically obligates you to take actions. When you do a bit of moral reasoning that leads you to believe that some action would be good to take, you should feel equally bound by the moral force of that reasoning, whether it implies you should donate your first dollar or your last. 

Do you agree with something like "trying to apply your axiology in the real world is probably demanding"?

Thanks for the links, Richard!

See my response to Scott - I think "obligatory" might have been a distracting word choice. I'm not trying to make any claims about blame/praiseworthiness, including toward oneself for (not) acting.

The post is aimed at someone who sits down to do some moral reasoning, arrives at a conclusion that's not demanding (eg make a small donation), and feels the pull of taking that action. But when they reach a demanding conclusion (eg make a large donation), they don't think they should feel the same pull.