Naming the waypoints after the coordinates is an interesting idea.
My rationale for having "L2" (or whatever) as a prefix was to group all the lane waypoints together in the listing on the GPS ... but I can't really see an overriding reason to do it that way.
The software I use is indeed MapSource, plus another package called Fugawi, which contains 1:50000 OS maps for the UK and has very similar waypoint / route / track functions as MapSource (but no auto routing). I think you're right about MS not knowing the difference between the comment and description fields - however we only really need one comment per waypoint (probably).
I think we need to thrash out a logical, but not overcomplicated, system for storing this information.
Thoughts on your naming scheme for waypoints:
If you've got the waypoint on a GPSR you can find the coordinates of it from the info screen anyway.
Ideally, every place a lane meets the tarmac, there should be a waypoint (this could be debated) to help people find the most convenient access point. I've been calling these waypoints something like "L1-Corwen5N" meaning the northerly access point to lane "corwen5" which is a difficulty grade 1. Of course character limits come into play here.
If the waypoints were named using coordinates (Clive's scheme) then waypoints allowing access to the same lane would have different names, and no obvious way of linking them.
I don't think either scheme is ideal ... but there's only so much information you can squeeze into 10 characters
Thoughts? Should we discuss this via email?