Feedback capacitor in comparator circuit with an OP-AMP
It helps to look at this in two independent ways, the instantaneous AC response, and the long term DC response.

In the short term AC case, consider the voltage across the cap as not changing.  Any step output will show up at the positive input attenuated by the resistor divider of (R2//R3) and R1.  This attenuates by 2.33.  A 30 V output step would therefore cause a 12.9 V step on the positive input.

In the long term DC case, just consider the capacitor open.  The feedback is thru R2, and attenuated by R1.  The positive input, your blue line, will always be close to ground since the R1,R2 divider attenuates by 670 times.  15 V on the output, for example, becomes only 22 mV at the positive input.

In between these two cases, the instantaneous AC effect decays to the long term DC effect roughly according to the time constant (R1 + R3)C1, which is about 300 &micro;s.

The labels on your graph are unreadable, so the numbers can't be verified.  However, the general shape of the signals is as expected.