Eli Zaretskii <eliz@gnu.org> writes:

> What column alignment do you have in mind, and why would it not be
> preserved without using the fringes?

I was thinking of a buffer containing source code with
outline-minor-mode enabled. The column alignment would not be preserved
since the emoji, SVG arrow, etc., whatever is inserted at the beginning
of a line but in the fringe, occupies horizontal space within the line.

Stephan Monnier gave an example.

> Do you see such a problem in the Customize buffers?

Customize buffers weren't in my scope.

I don't know if it's related to the arrow but I find their identation
strange: The settings aren't indented but their description is indented
by three spaces and doesn't align with the first non-white space
character following the arrow.