Staring at it longer, I think marcan's right - there are duplicated lines on the "o", but if it was NN the whole column would have to be duplicated, and it's not (look at the top and bottom of the "o").
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Exactly, that's what I was going for. NN is always row/column-wise and leads to fairly obvious horizontal/vertical discontinuities if you look closely. That is not the case here.
This is what happens with no/bad hinting (not your actual glyph, but you get the idea)pic.twitter.com/MEJq4mVEuv
