Selection mechanisms are of interest to me because I suspect as some point I'm going to be looking at defining a custom one for mathematical documents. Most input can be icons, key bindings, or both (e.g. Ctrl-f for a fraction) but selecting mathematics for various operations will be a challenge. (This may ultimately be one of the harder problems associated with 2D mathematical input, as I understand it, but not having tried it I can't say for sure.)
I wish I knew enough about this to have an opinion - I guess I need to read the spec for a while and see if I can get it to "click".
CY
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