chains that come with masterlinks arent meant to be broken like that... the rivets are not the same as say a shimano hg chain
take sram for example it comes with a master link and if you break it you will see shavings etc... this is because when manufacturing the chain the rivet with a machine that presses the sides..
now when you break a chain to cut it down.. you bail the pin and use the master link to connect the two therefore creating no points where the sides have been "sheared" so to speak
when you shear the sides, you create a weak spot .. now torque that bad boy, and the pin will want to move within the chain later pulling out from the plate.
even with hg chains the pin that you press in has a side that is "flattened" out so to speak, and the other side, once you break the pin, is positioned further out.. so any movement from the pin wont, usually cause a failure.., unless you are breaking an old chain which has stretch... with that said never break/ or try to repair an old chain with stretch over 1/8in