Hello Brad,
On this issue, I’ve noticed a particularly egregious example in the
past few days: around 20 ppem, with autohinting enabled, ⟨ñ⟩ in Noto
Sans Regular consistently renders with a horizontal bar, so as to be
indistinguishable from ⟨n̄⟩. As Werner mentioned some time ago, this
particular character may not be a huge problem in practise, but it
would be nice to get this fixed nonetheles. I note especially that
--- at least on my machine --- popular sites like Wikipedia and
Reddit render in precisely this font at that size.
I think – hope – this is on Craig's plate :-) And yes, the tilde
character needs special treatment, i.e., a vertical exaggeration of
the shape for small sizes to retain the wiggle.
Werner