For me positive comments aren't a big deal in a well-upvoted, uncriticized post, but create a buffer against the stress of harsh criticism in a way upvotes do not.

I prefer comments to upvotes, upvotes feel like mindless applause lights. Contentless comments still tell me something about who found it helpful and how much (length of comment as proxy)

Good question!

Yes, and probably. The comment makes me feel more rewarded for whatever effort I put into the post.

I do appreciate the little comments but for me there's a huge benefit for even a sentence of why they liked it.

For instance this comment definitely had a much larger positive effect on me than a strong upvote:

I really appreciate seeing this kind of applied statistical analysis to a stray interesting-sounding fact you heard.

I doubt this took much longer to write than "Good post!" but the extra time was definitely worth it to me.

So, querying my preferences a bit more in depth:

• I think literally "good post" mostly just feels sad. The variations that I appreciate sometimes at least type out a sentence or use less frequent words, which provide some evidence of the person engaging with the work, or... I dunno maybe it's a just a "costly signal of fashion" thing. "I don't have anything to add but just wanted to say I found this post helpful" crosses some threshold from "neutral or slightly negative" to "slightly positive."
• If there are more than three "mildly fashionable 'good post'" type comments as described above, it switches from feeling net positive to net negative for me (unless there's a lot of other comments that are more substantive)
• If I post something, and a few days go by with zero comments, and then I finally get a comment, and then it turns out to be mostly contentless, I experience a tiny-roller-coast of "ooh! a comment!" .... "oh, it's a lame comment" ... "okay upon reflection I'm still glad someone did that because it makes the comment section a feel a bit more alive, or at bumps it up in recent discussion, which gives it another shot at actual conversation.
• If it's been years, and then someone comments on an old post of mine that hasn't been discussed in awhile, I feel mostly good and a bit nostalgic. ("Oh, people are still enjoying that post!")

I've felt happy about all positive comments, regardless of how substantial they are. Making a comment always takes more effort than just clicking upvote. Of course, more specific praise that gives me a better idea of what someone liked about my post is even better.

Comparing with a strong upvote is hard though, ideally I'd prefer both.

Yeah! I like getting positive feedback on my work, especially in a rather intimidating forum like here. Anything more specific than "good post" or whatever is better, but even that is more emotionally rewarding than seeing digits in the vote box change.

Yes to both, but I'd still rather get comments that are interesting :-)

I like comments that don't look like they could have been generated by a chatbot. I feel like whenever I'm being fine with the "Good post!" comments, I'm setting up an environment where after a while a portion of the comments will actually be chatbot spam.

No. I would rather receive a strong upvote. If I receive a comment I would prefer it contain some useful content.

I don't get any value out of content-free comments, but a sentence or two explaining what someone liked about my post gives me better feedback than an anonymous upvote. And even if it's just a phatic "Good post!", just knowing who said it can be quite useful.

If there are no other comments, a "Good post" can help the comments section feel less empty, make it feel like someone has actually read it. 

If there were several substantial comments and a mountain of content-less ones, then I suspect that the content-less ones would feel like a waste of time, but this hasn't happened to me.