It's still possible for two commits to conflict only semantically, one obsoleting the other. Merging both would lead to dead code so perhaps stricter (line-base or ast-based) conflicts would be preferable.

You're right, that's a real risk, weave runs post-merge validation for exactly this, it checks entity dependencies after merge, so if one side obsoletes what the other side depends on, it warns you even when the textual merge is clean