The number of devs who screws up rebase, or worse merge, is astonishing. "I just used theirs" :|
You're right, there are a lot of devs like that. In this day and age of DVCS any developer worth their salt should be able to manage merges properly. It sounds like SO might not hire people who are incapable of understanding merging.
If your code is well organized into modules broken down by functional area, it should reduce the number of potential conflicts.
Also, fear of merge conflicts is somewhat unjustified; most conflicts can be resolved and rebased against using git rebase without that much work; the git rerere option [1] and git imerge [2] can also help with this.
If developers would actually learn how to resolve merge conflicts, and not be afraid of the occasional conflict resolution which requires understanding the other change and how to write new code that incorporates both changes, it's less overhead than communicating about pending changes.
[1] https://git-scm.com/docs/git-rerere [2] https://github.com/mhagger/git-imerge