ok i copied the unmodified libwebkit-1.0.so.2.5.0 from my k4, hex edited it to replace the only instance of "_blank" with "_blonk", and the first instance of "target" (as a whole string, null bytes at each end) with "tbrget", and it seems to work as the downloaded hack did on the sites i've tried, eg gmail basic html, can follow links. this time the text entry works too where it didn't before, eg. gmail's login.
fingers crossed not too many other problems will rear their heads any time soon
edit: i still don't know what might be changed in the browserd from the download, can't compare without figuring out what firmware version it was from and locating an unmodified version, but doesn't seem urgent.