Zero-Width Characters
Homoglyph Substitution
Detectability
Trivially flagged by any Unicode scanner or hex editor. The non-printable code points are a dead giveaway.
Harder to catch without a Latin↔Cyrillic reference. The characters render identically, and most spell-checkers accept them.
Bandwidth
High: any carrier works. The hidden stream is carrier-agnostic and scales with message length.
Low: capped by the number of substitutable characters in the carrier. Only 21 Latin↔Cyrillic pairs exist in this implementation.
Robustness
Fragile. Slack, Twitter/X, and many email clients strip zero-width characters before storing or displaying text.
Durable. Cyrillic lookalikes survive copy-paste on essentially every platform. No common stripping heuristic targets them.