Hi, thank you for the response, I appreciate it.

My initial goal with the crossing=no tag was to instruct routers not to have pedestrians cross here, rather than e.g. to communicate with other mappers that there really isn't a crossing here.

Routers incorrectly routing on the road rather than the sidewalk and crossing the street in unsafe places rather than on crossing ways is still an issue today, e.g. https://www.openstreetmap.org/directions?engine=graphhopper_foot&route=43.723463%2C-79.458302%3B43.722979%2C-79.456049 (and it's the same with all 3 routers on OSM.org: GraphHopper, OSRM, Valhalla)

But I think I see the issue you're pointing to: with a crossing=no tag at an intersection, a router can't know if they shouldn't route pedestrians along one street, along the other, or both. And in this case, routing along Dufferin Street would be valid, as long as the side of the street isn't changed.

And while I would say that a good pedestrian router shouldn't route along Dufferin Street itself given that sidewalks are mapped along it, equally, that good router wouldn't route along Dufferin Street to get anywhere from the T intersection.

So tagging the intersection itself crossing=no would be ambiguous for any router that attempts to read it, and not needed for a router that correctly prefers sidewalks.

And tagging crossing=no north and south of the intersection would only be useful for communication with other mappers, since it wouldn't change the situation for the routers. And at least in Toronto we haven't had a problem with mappers mapping crossings that don't exist, so I don't think it's particularly important to do so.

So I don't think a change here is really necessary now.

Thanks again!
--Jarek