In vim filetype, " has two roles. One is a string literal, and the other is a comment sign. So that the ideal behavior is to:
The current default rules doesn't care about inserting comments.
Since the syntax of Vim script is too arbitrary as a programming language, it's hard to guess the current context perfectly. Therefore we have to use a simple-but-imperfect method to cover practical usage as much as possible.
An idea: Most comments are written in their own lines. Inline comments such as :foo " bar are not frequently used.
:foo " bar
Merge branch 'for-authoring-vim-script'