For ardour, we almost never squash commits because we prefer our (always linear) git history to show the actually "story" of a branch's development.

There are two exceptions.

1. branch developer suffered from several "thinkos" along the way, the branch doesn't contain that many changes, and there's simply no benefit to seeing the contrast between the initial (mistaken) changes and the final result.

2. the branch commits create a situation where git bisect can't be properly used because intermediate commits will not compile. Squash is one option here, though it is often preferable to just re-branch and re-work commits to avoid both the bisect problem and the squash.

With a 21 year development history, we have found it invaluable to be able to trace the "thought processes" behind a series of commits, and squash would rob us of that.