It's remarkable the number of people making excuses for Hillary's torn-end finish last night.
She didn't "extend", or fail to concede, plausibly for most of the reasons given.
She extended in order to judge the strength of her ability to carry onward. She made an appeal for money and support, last night. (Presumably that wasn't so disingenuous as to be just about retiring past debts).
This is partly a problem with races that have indeterminate rules and are allowed to continue, by "consideration" or by artifice, past when they ought to have ended.
The rest is noise.