Since we both recognize the U.S. as a pathological case, I’ll point out that we haven’t adopted maxspeed=implicit here because it preempts any numeric value. Shifting the burden to data consumers would be counterproductive, because they’d face even more challenges interpreting the law. To the extent the community can figure out the applicable speed limit, we’d like to save others the trouble of figuring it out for themselves.
We should only map a negative if there’s a clear use case for it. noname=yes and similar tags are popular because they enable very useful validation rules. I promote not:building=yes and demolished:building=yes in order to warn armchair mappers to think critically and warn data consumers that they shouldn’t backfill buildings from lower-quality sources.
Apart from StreetComplete’s interaction design, I don’t think the absence of speed limit signs on the spot has such a clear use case. What would a mapper on the ground be trying to communicate to data consumers or other mappers? It isn’t like the No Traffic Signs sign, which would be some sort of hazard=*. It’s more like: “StreetComplete asked me for the speed limit and I can’t easily tell.” MapRoulette has a similar Too Hard button, but it stores the response in its own backend instead of the OSM database.
