Hey,
yes very helpful for me too!
I am thinking about using streetcomplete (adapting it) to encourage the contribution on accessibility topic (for mapping parties and extra if participant get passionated J). I would love to share experiences once we have tested a bit more. Happy to read Sam that you have experienced that kind of projects, I would also love to have your feedbacks and maybe recommendations… Have you hard about the Cartomobilite project in France? It was initiated by association Tiriad, I can share contacts if you are interested too, it’s also about mapping accessibility into OSM with people with disabilities. Huge parenthesis but great connexions I guess 
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@Adam, I would be curious to know how you would suggest to map connexion between sidewalk and crossing as in the wiki, highway=crossing is supposed to be on a point of a road. Then would be the projected point on the sidewalk (hope i am clear), the place to put kerb info? For now I indicated wheelchair accessibility (directly connected to kerb) and blind accessibility on the crossing. Maybe it would be best to add it at the projected point on the sidewalk then?
Plus as your are saying that ORS algorythm is taking kerb:height into account, would it be an option to use kerbe=raised or lowered also as it has a link with height? I think it is easier for people to use that as less precise. (you don’t always have a measuring tape with you).
Hope I am clear,
Look forward to reading you,
Best,
Violaine