People can only go on what you've given them and with little context (examples, etc) they're going to question some of the decisions made, i.e. the character class:-
pat = re.compile(r"<!--docstart -->[\n\w\s<>.\"/_=-]*<!--docend -->$", re.IGNORECASE|re.M)
as most people would just expect to do:-
pat = re.compile(r"<!--docstart -->.+<!--docend -->$", re.IGNORECASE|re.M)
It all depends on information they don't have, i.e. are any lines likely to contain extra docstart or docend tags, are some lines to be rejected because of invalid/unwanted data, etc.
Without that context a character class such as [\n\w\s<>.\"/_=-] is a red flag to me, especially with the \n in there (before the regex was in multi-line mode). Another red flag is the lack of a start of string anchor given the presence of an end of string anchor - both or neither in general (but, again, I don't know the full context).
If it's just a set of lines that need converting and the list will be checked afterwards then there's little point over-engineering a one off task. If it works, move on. If it's something that will be run again and again (as part of a release) then I'd expect something a lot more defensively minded.