Frankly, it depends how the engagement is set up? The Frank White trigger on my AR comes with moly grease all over it, and the recommendation to use more of the same. Works great. I set up my 1911's with a slight overhang of the hammer hook so they are mechanically safe whether oil gets in them or not. It will do so accidentally in most any semi-auto, as they tend to blow lube and smoke and graphite and all the rest all throughout the gun. Many other guns will get lube creep or accidental distribution, so it is best to have a trigger that can tolerate some lube.
If you like a crisp trigger, most mechanisms depend on rapid slip of the engagement going from a static to a kinetic coefficient of friction, the latter being usually about half the former. But if you put a lube film there or let Teflon or other dry lubes accumulate in the engagement, the difference in the friction coefficients will be reduced and the trigger can lose crispness, engagement weight, and even start to creep in some instances.
An example of a mechanism that would not like lubrication is the older Savage pre-Accutrigger still in use on the Stevens models. I replaced that factory trigger on my 10FP with a Rifle Basix trigger and set it up a bit lighter than the factory trigger was out of the box. The result was one incident of discharge on closing the bolt (gun pointing downrange at the berm). I increased the trigger release weight a half a pound and gave it some jostle testing and it was fine after that. I later replaced the trigger again with the Sharpshooter Supply trigger, which has allowed safe lighter engagement. A friend with that same rifle and the factory trigger also had one discharge on closing the bolt. I think he messed with the springs or some such thing, so it also had to go back to original condition. But the bottom line is that trigger mechanism is not one you want to lube. It runs too close to the edge of safe to begin with.
On the 1911, I've also had occasion to clean one out for a fellow competitor whose wad gun had doubled on her. She never tore the the down, I guess, and over a period of years it had built up so much powder residue that it was caked with graphite/carbon mix. The trigger broke without creep, but felt slightly mushy and the hammer followed the slide on closing. The graphite/carbon mix had actually accumulated at the corner of the hammer hook to the point it was reducing the engagement depth, and it was actually lubricating it. I didn't have a trigger weight with me, but suspect it was too light. So, I gave it a good de-caking during the match lunch break. The trigger crisped right up and the hammer stopped following the slide on closure.
In her case, additional lubricant might have made the hazardous situation worse or it might have cleaned out some of the carbon? I don't know which would have happened?
