It is not possible to "-1" or to "+2" a diff in Phabricator exactly like you would do in Gerrit. Then again, we seem to have all the pieces in place.
- Possibility for All Users to add positive/negative comments and symbols (+1 and -1 are in fact symbols, not votes, since the decision over a review is not based on counting votes).
- Possibility for the maintainers of a repository and only for them to reject or approve a diff, the later action implying the merge of the diff (triggering whatever CI process we have in place).
- Possibility for anybody to abandon a diff, and recover an abandoned diff.
To be clear about policies: users should not be able to merge or reject a diff in a repo, unless they are the maintainers.
Are there other scenarios related with evaluation of diffs that we should consider?