When setting "formatOtherKeys" resource to 1 in xterm, 'CSI u' format is used for non-standard keycodes. This is also how mintty support "modifyOtherKeys" by default.
But in term/xterm.el, only 'CSI 27" format is supported.
I think it is worth supporting "CSI u" format control sequences.
What do you think of adding them to teerm/xterm.el? or anyone can do it?
/Victor