>>davidb+(OP)
The "Texture Healing" feature is a really smart use of OpenType features to make problematic monospace combinations look much better without breaking the grid at all.
One naive way to do this would be to create ligature pairs for difficult pairs (mi, lm, etc). But instead, they seem to be selecting character alternates that fill the fixed width differently based on their surroundings.
>>turnso+B7
Meh... not convinced. Once you have toggled the checkbox a few times, you start noticing inconsistencies: e.g. in the example shown by default, the second "m" in "time_limit" is obviously wider than the first one because it has more space to "grow" having "i"s on both sides. Not sure if I like this...