[saucetenuto]

Suppose I have a configured tab width of 2 and I write a line with three tabs that's 78 characters wide. When my friend with tab-width 8 views it, he'll see a line that's 90 characters wide. What do projects with 80 character limits do in situations like that?

In either case the line contains only 75 characters, of course, but that's a pretty pedantic non-answer: we care about horizontal screen space, not the number of bytes of storage you'd need.

[scrollaway]

EditorConfig tells you the canonical tab size for the project, in other words "a tab counts as 4 characters to the soft wrap". If you choose to increase the tab size beyond 4 characters, you have to accept you'll get longer lines.

(It's also high time we stop pretending wrap limits matter to the exact character. In most cases, they are and should be guidelines - we have evolved beyond 640x480 CRTs and 80 character terminals)