Differential amplifier with feedback resistor

In this circuit, if a resistor of 1 M$$\\Omega\$$ is connected between A and B, what is the effect on the stability of the quiescent point?

The analysis I made led me to believe it would provide positive feedback and thus won't stabilize the point, but I dont feel safe enough as to assure it. Which is a good method for verifying this? I couldn't think of a way to check it in a circuit simulation

• This simulator works tinyurl.com/y6ybgh77 drag 1M into position and see gain ratio – Sunnyskyguy EE75 Feb 23 at 22:50
• That's a really useful simulation, but what I'm interested about is the stability of the operation point rather than gain – MPA95 Feb 23 at 22:57
• Change one of the gain bias resistors and see output offset without feedback and with reduce due to H gain – Sunnyskyguy EE75 Feb 23 at 23:03