ViEmu does support cf" (I would know, since I wrote it). It means "change up to and including the next double quote", which is indeed classic vi, and supported

ViEmu does support cf" (I would know, since I wrote it). It means "change up to and including the next double quote", which is indeed classic vi, and supported by any non-trivial vi/vim emulator. I would guess the author of the author of the article meant ci" (change the text inside double quotes), which is vim-specific rather than vi (even a recent vim version, not an old one). ViEmu also supports that, but I'd guess many other emulators won't. Indeed supporting a large part of the vim commands most people use is no walk in the park. I started writing ViEmu in 2005 and I'm far from running out of oft-demanded commands and motions to implement.