Seriously, this is the heart of it. The one thing about Emacs that I just can't forgive is its insistence over the decades on mixing tabs and spaces in its auto-indentation.

Ultimately, the spaces vs. tabs debate really comes down to which policy is less likely to result in mixed tabs/spaces. If people use tabs, it seems inevitable that some spaces will sneak in there as well. If people use spaces, tabs are unlikely to sneak in. Obviously that's a combination of common default editor configs and human behavior, but that's just how it works out in practice.

this is my opinion, too. In an ideal world we would all use tabs so that we could all see the indentation level that suits us best. But it's not an ideal world. So we're forced to use spaces and agree on how many spaces to indent with.

Except for Go programmers.

Tabs for indentation, spaces for alignment. That's the only acceptable mixing.

It works because it allows everyone to configure their code editor to have tabs be whatever width they want without messing up how it looks for other people.

But it's futile. Unless there's a git hook setup or you're using Python 3 which throws errors when tabs and spaces are both used for indentation, you're gonna end up with source files with both being used.