I think that you've put it very well Rhubarb.
I do have some sympathy, he does seem to put a lot of work into his writing, and he is being honest about what kind of barometer he's using to judge the audience feedback. As with Rhubarb, I don't expect that sort of response per chapter either, but I do have an idea of the number of views/readers I seem to get.
I suppose it's about what he values about what he's doing. There is a lot of pleasure in thinking up a story, working out a plot and finding a way to put it across. But if that were the only pleasure no one would ever publish anything. There's a pleasure in sharing your work, and in (hopefully positive) feedback, but if you feel that's waning you might not feel motivated to finish.
I should say I haven't really enjoyed his last story and stopped reading it a few chapters ago. Partly it's a taste thing, I find them quite long and slow moving, but also because I'm writing my own at the moment I'm rather selective about what I read, (and this is going to sound pompous, sorry) because I have my version of Molly & Charles in my head and I don't want to be thrown off by reading someone else's.