Possible ways of protecting comparator input from coupling?
So to close my own question, this was solved by the insights of noise on a trace given here

The oscillation happens because of parasitic capacitance between the output of the comparator and it's negative pin. Since I've had the input resistors of this pin close to the source, instead of close to the input, the signal source had a bad time trying to reject the induced noise.

This was solved with better layout and normal hysteresis.

Others solutions that would solve the issue would be lower value for those input resistors (lowering input impedance), or a better comparator IC with much higher input impedance - like the TLC372-EP (bigger output impedance)