An autoformatter wont touch a tabbed ASCII diagram in the comments,

Go's autoformatter will absolutely screw up existing ascii comments when they randomly decide to change how the formatting works.

As found the hard way when one day we updated the version of the Go formatter, and much of our nice comments needed to be redone. Thanks Go formatter team (yes, that's being sarcastic).

but the autoformatter will have dictated the choice of space vs tabs for the file in question, an likely also the width of tabs (if any) for alignment. so you just need to follow the convention.