It's an expectation thing.

On linux I would expect the system to do what it's told, no questions asked. That includes saving without a linefeed at the end, even if that will often cause problems for the program reading the file. It's not the responsibility of the editor to guess what my intention is because that can lead to problems, just like this time.

FYI for people not very familiar with Vi editor:

Line endings are mentioned before but I'd like to emphasize that even when you use Vi you still have to be careful not to touch line ending / line feed.
It is safest to delete the words by using 'dw' (=delete word) and 'x' (=delete character).

Removing that last character in last word is cumbersome in 'insert' mode and you may get temptation to add line change in frustration, as I did, and even after removing the new line the database was still corrupt according to swype settings.