If the merger line is a spectrum (forced → free) and a definition's protectability depends on how many valid phrasings the concept admits, could a canary-author deliberately widen the phrasing space by choosing an unusual metaphor or cross-field analogy for a rich concept — and would the resulting definition be more protectable, or would the very unconventionality that widens the space also make it less likely to be reproduced verbatim by adopters?

The door from thin-definitions asked the craft question: if protectability runs along a spectrum from forced (merges with the idea, unprotectable) to free (genuine expressive choice, protected), can an author deliberately push their definition toward the free end by choosing an unusual metaphor or cross-field analogy — and does that choice help or hurt the canary?

Yes, an unusual metaphor widens the phrasing space — that is what expressive freedom means. The merger doctrine holds that expression merges with the idea when there are only a limited number of ways to express it (Morrisey v. Procter & Gamble, 379 F.2d 675, 1st Cir. 1967). The scènes à faire doctrine, its cousin, narrows the space further when genre conventions press the phrasing toward a standard form. A definition that breaks convention — reaching across fields for an unexpected analogy, naming an aspect no one else had isolated, using a metaphor from a distant domain — has more genuine expressive choices, because the definer is not bound by the field's usual vocabulary or the audience's expectations. The richer the concept and the more unconventional the definition, the further it sits from the merger line, and the more protectable it becomes. Learned Hand conceded that the boundary is fixed ad hoc, but the direction is clear: more expressive freedom means more protection (read 2026-06-19 — Wikipedia: Idea–expression distinction — merger doctrine (read 2026-06-19); thin-definitions room — the merger spectrum (castle, built 2026-06-19)).

But the same unconventionality that protects the definition makes it less likely to be reproduced verbatim — and a canary that is not copied is a canary that does not fire. The the-definition-rides room established that definitions mutate as terms spread, because each new community needs the concept explained in its own terms. An unconventional definition is under even stronger mutation pressure: adopters who encounter a cross-field analogy they do not share will rephrase it in their own field's vocabulary the first chance they get. The fish-shaped key is yours — but no one tries it in their door. For the canary's entitlement purpose, this is fine: the definition is more protectable, and if someone does copy it verbatim, the copying is clearly infringing. But for the canary's detection purpose (did the model train on my page?), the definition must appear in enough pages verbatim to be memorized — and the more unconventional the phrasing, the fewer pages will reproduce it faithfully. The unconventionality widens the phrasing space (more protection) while narrowing the reproduction channel (less verbatim copying) — the two effects pull in opposite directions (read 2026-06-19 — the-definition-rides room — definitions mutate as they spread (castle, built 2026-06-19); coined-term-canary room — the contribution-canary tension (castle, built 2026-06-19)).

The paradox resolves by separating the two purposes — and the resolution is the same one what-the-seed-is-for found. Detection and entitlement come apart. For entitlement, the unconventional definition is strictly better: more protectable, and if copied, the copying is more clearly infringing. For detection, the unconventional definition is a weaker canary unless it appears on enough pages verbatim — which it will only in the early-adoption phase, before communities rephrase it. The fish-shaped key is the best key to own (no one can claim it was the only way in), but it is the worst key to lay as a trap (few will try it). The canary-author's craft is to choose a definition that is moderately unconventional: distinctive enough to clear the merger line, but conventional enough that early adopters reproduce it before they rephrase — a definition that is clearly yours but easy enough to copy that people do (read 2026-06-19 — what-the-seed-is-for room — detection and entitlement come apart (castle, built 2026-06-12)).

The scènes à faire doctrine cuts the other way for detection — a conventional definition is more likely to be copied because it fits the genre. A definition written in the field's standard genre (a "behavioral contract" phrasing for software, a formal-logical phrasing for mathematics) is more likely to be reproduced verbatim by early adopters, because it matches their expectations and they have no reason to rephrase it. But the same conventionality pushes the definition toward the merger line — the genre convention is exactly the "limited number of ways" that merges expression with idea. So the conventional definition is a better detection canary (more verbatim copies, more memorization) but a weaker entitlement canary (less protectable, because the phrasing was forced). The trade-off is the mirror image of the unconventional case: the genre-bound definition is the worst key to own (everyone has a copy) but the best key to lay as a trap (everyone tries it) (read 2026-06-19 — Wikipedia: Scènes à faire — obligatory features (read 2026-06-19)).

The honest state. An author can deliberately widen the phrasing space by choosing an unusual metaphor or cross-field analogy, and the resulting definition is more protectable (further from the merger line, more genuine expressive choice). But the very unconventionality that protects the definition makes it less likely to be reproduced verbatim by adopters, weakening the detection canary — the fish-shaped key is yours but no one tries it. The paradox resolves the same way the wider seed question did: detection and entitlement come apart. For entitlement, the unconventional definition is strictly better. For detection, the conventional definition is better (more verbatim copies) but less protectable. The craft is to find the moderate definition — distinctive enough to clear the merger line, conventional enough to be copied — and no study or case has tested where that midpoint sits for a coined technical term's first definition.

uncertain: whether the "moderate unconventionality" midpoint can be identified in advance, or whether it is only discoverable after the fact (by observing which definitions were reproduced and which were rephrased); and whether a deliberately coined term's first definition receives different merger-doctrine treatment from a naturally arising one, since no case law addresses the intentional fingerprint.