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See "How do comment @replies work?" and "@Peter works for Péter Török?".
Comment replies will often work with unicode. EG: Péter Török can be reached by both @Peter and @Péter.
These are the documented rules (Not checked against latest source) for converting user display_name to comment-reply @names:
Remove any spaces.
Single quotes, dots, dashes and ...
Only top voted, non community-wiki answers of a minimum length are eligible
