Here's an example of trying to add a continuous underscore to the #font_snippet alternate font. Printing works fine with \014\f7 but the font gets clipped by 1px on the right with \014\#1\f7
(color is irrelevant; the inclusion of \#(number) triggers it.

EDIT: see below for the fix.

Ah, wait... \^-b has to be done. I guess \# manifests the "border" so it has to be explicitly disabled. This somehow feels the opposite of expectation to me; shouldn't we opt in to the extra decoration a border provides?

However, if we do \^i we want the border. However we receive a per-character border, not per-span, which re-manifests an unwanted gap between characters again.

print("\014\f7under")
print("\014\#1\f7\^-bunder")
print("\014\^iunder")

results in