hah. nice post.
i saw that demo on the front page of the site and immediately wanted to try it as well.
in retrospect, it possibly might have made more sense to label that menu option (cmd+shift+l) "split cursor" instead of "split lines". i think that more accurately describes what the text editor is doing in that case.
the ability to split a line selection using a quick search/regex would be really helpful for that very purpose. with all the support for python, it'd be interesting if one was able to hit a key-combo which brings up a text box to execute arbitrary code. something like:
the cursor split and line join options are great though. although it took a few attempts to figure out how to split the lines in the first place (find/replace on just a single line). i half expected the command options to be consistent with other GUI editors (+F for find, +R for replace). instead, those commands seem to be a little jumbled around (possibly for familiarity with legacy text-based editors). additionally, some options in the same UI are alt+cmd+something vs. ctlr+alt+something (select regex expressions vs. replace all for exmaple). some consistency there, or context-sensitive options to reduce the number of key combinations required, might help simplify things.
all minor, and just a matter of not being familiar with the editor's idioms yet i guess. i imagine those can be corrected with keybindings, but typically that won't be reflected in the menu options (unless those are dynamic and not compiled in).