Quick Release on Horizontal Dropouts
 

Is it bad to use quick release skewers with horizontal dropouts?

No. Why do you ask?

No, but use the steel ones, not the alu ones, they do not provide the needed "grip".

Since horizontal drop outs are really diagonal, i thought a sudden impact from the road might push the skewer back if they didn't tighten up enough to withstand the force.

Modern QR are not as robust as they used to be when the axle was not in a mere notch, so make sure it is a steel one. And make sure the ends of the axles do not extend out past the outside of the frame. And make sure it is good and firm. Otherwise not a problem.

jim

use shimano or campy offset cam lever QRs
if it's a chromed drop out, turn the nut a bit tighter than usual.

+1 on using steel ones. Also, push the axle all the way back or align it properly with the aligning screws.