After a few tries I found something that looks a little bit strange to me: the Insert mode meta keymapping actually works, *only if* you set at least one mapping with the leading <Esc>.
Previously I tried my best to avoid mapping the <Esc> leading keys, although it works, because it would introduce ambiguity and get Vim stuck when <Esc> was pressed, but all the <M-...> mappings wouldn't work then, like they were all ignored. Now I've found this: inoremap <Esc>m <nop> with this key mapping in place, suddenly, all my <M-..> mappings in Insert mode works! But this mapping still introduces ambiguity to the Escape key, a dilemma ... -- -- You received this message from the "vim_use" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_use" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.