In-Context Editor can't handle implicit index.html

The In-Context Editor can't handle implicit index.html - e.g., when a menu link points to /subfolder/ with a file named index.html inside, the link works fine on the front-end but In-Context Editor users get a 404 Page Not Found error.

Naively, it appends .htm to the folder, producing an invalid url like this: /subfolder/.htm

The workaround is to explicitly include the filename in the link like /subfolder/index.html, but this is undesirable.

Anyone else been bitten by this?