will-i-am (2020-05-24 18:08:42+00:00): Hi Richard

I will try to address your observations:

    You say "You need to add bicycle=yes and foot=yes on the way to make it clear.  Route relations are additional information; they don't obviate the need to have the correct way tagging.""
        https://wiki.openstreetmap.org/wiki/Way says "A way is an ordered list of nodes which normally also has at least one tag or is included within a Relation."
            my take from this is
                that the tagging can be applied to the way or the relationship to which the way belongs.  Tagging the relationship facilitates tagging because instead of having to tag every way, you can tag the relationship once and the modification will ripple down to all ways in the relationship.
    https://wiki.openstreetmap.org/wiki/Tag:highway%3Dpath
        This tag is used for paths for which all and any of highway=footway, highway=cycleway and highway=bridleway would be inappropriate or inadequate (or simply not sufficient),
    You say "In the route relations in particular, note that the semicolon-separated style you've used ("route=hiking;bicycle;foot") is idiosyncratic and undocumented, and most renderers/routers will not understand it."
        I learned about the semicolon from Sarah at waymarkedtrails who commented to me that "this is a topic where there is not a complete agreement in the community. Multiple values in a tag is indeed a bit problematic for data consumers and many don't support it.........these routes are explicitly marked for multi-use and that is something we should map as it is. I was not able to come up with a better idea than the semicolon version,so decided to support it in waymarkedtrails. It's up to you what you do with it."

It appears that we are working in a highly dynamic, evolving environment and dealing with extraordinary complexity.  It is clear to me that the coding of the data is of paramount importance.  It needs to be properly encoded and easily maintained; something tagging relations, where possible, rather than individual ways does facilitate.  If the data is encoded and maintained properly, the renderers can be easily modified to render the data properly.  The waymarkedtrails site provides several different views of the data.  When I started working on osm in 10/2015 mostly in the NJ - NY area the map had many "ways" but virtually no "relationships" and no use of the "osmc:symbol" https://hiking.waymarkedtrails.org/help/rendering/osmc.

    It looked pretty much like this link from an area in which I have not worked
        https://hiking.waymarkedtrails.org/#settings?map=16!43.5228!-71.3649
    The areas I have worked on look as they do at the following 2 links because of the use of relations and osmc:symbol tags.  Here are 2 of the same area: 
        showing the hiking trails (click the "Route" button in the lower right corner)
        showing the mountain biking trails (Click the "Route" button in the lower right corner)
        Sometimes one trail is both hiking and mountain biking.   Sometimes they are hiking but no biking.

Bringing millions of contributors to a consensus concerning best methods for encoding data is a chore because in essence we need to learn to speak the same language and adopt best practices to accurately reflect the realities.  This will take time and I am guessing that "most renderers/routers" will learn along with us.  Exchanges like ours is a key part of the process.

Thanks.

Bill