> Squashing makes the diffs much more painful, such as by burying an important change in a sea of mechanical ones when they were originally in separate commits.

Can you give an example? I don't even think I understand what you're saying. You control your overall summary, so it's up to you to make it useful.

I would cite clarity as my reason for squashing! I think most people are just bad at organizing (& naming) their commits, so they make A LOT of vacuous ones, crowding out the forest for the trees. It's never helpful to see the git blame saying things like "Addressed PR comments" or "Resolved merge conflict", etc.

I do prefer a merge commit when the author has done a good job with their own commits, but that's rare. In all other cases, squashing is greatly preferable to me.