[emn13]

git could simply prevent you from committing to that branch in that case, and perhaps print a warning when adding a worktree. The current behavior is weird. Another alternative is to allow the commit, but leave it in a detached-head state, and let the user choose how to fix that retrospectively.

The way I use worktrees I'd say the majority are read-only anyhow, so abiding by restrictions because it might get confusing if a commit were made is pretty annoying.