I would really like to enable squash-merging via the GitHub UI.

1. The main benefit here would be keeping the Git history cleaner, especially since it allows for editing commit message while squashing.
   This would allow to have something more meaningful instead of the following easily:

 M─┼─┴─┘ Merge pull request #4307 from fzarifian/fzarifian-pr4304
 │ o Update AUTHORS
 │ o Fix linting
 │ o Improve changelog a bit
 │ o Update __init__.py
 │ o Create 4304.bugfix.rst
 │ o Update __init__.py
 │ o Add test to branch
 │ o Update __init__.py

2. It makes git-bisect behave better (less commits in general, no commits that need to be skipped because of failed tests (e.g. if refactor callinfo to simplify ctor magic #4299 gets merged as-is)

While you can rebase/squash things yourself and force-push, it will a) trigger an extra CI build and b) it cannot be done for other contributors PRs easily.