@rosettif It's actually a kinda neat idea to support touchscreen in a way that even legacy apps can use it. And anyway, for me, it seems touchscreen events and lightpen stuffs are kinda similar: not that 100% position accurate in nature, so it even fits well because of this ;-P And if I remember well, even BASIC 10 supports (?) it with LPEN(), so some can use it from BASIC too (same for mouse btw - it was a surprise for me, who was used to BASIC 2 with all the POKEs and PEEKs).
BTW: Interestingly, in ROM v0.9.910111 LPEN() functions expects parameter 1 or 2 it seems, while documentation states 0/1. As far as I remember there are other places too, where there is this conflict (maybe later ROMs corrected that, I haven't checked).