[WorldMaker]

2 is the base indent of the line where the : was added. Autoindent adds 4 spaces for the current tab stop. Autoindent isn't using some counts of indents, it's taking "spaces in previous line + tab stop".

Backspace doesn't unindent in vim by default, it removes spaces one at a time. That's a difference between the ts=4 (tab stop) and sts=4 (soft tab stop) is sts also applies to backspace. But the default is that it doesn't because the out of the box default believes that backspace operates on physical characters (spaces) not soft/fake ones (tabs expanded to spaces) by default.

I don't know if that is the right default, and it is definitely a baroque exercise to get all the settings right for some languages, but there is a consistency to the defaults even if those defaults don't meet some modern expectations from newer code editors.

(Also, I just realized above I confused tw [text width] and ts [tab stop]; my vim skills are rusting a little.)

[Dylan16807]

That doesn't explain how it then goes to 8 total spaces.