Suppose the Haftorah reader makes a clear mistake reading a word and it changes the meaning of the word. He is standing on the bimah alone and correcting him would require speaking up from your seat, which is several rows away from the bimah. He is not reading from a Tanach or klaf. (Later, we can deal with the fact that no one else in your shul of 60 men seems to be paying a bit of attention.)

Is it appropriate to correct him?

If correcting is appropriate, would you have the guts to speak up?

Is the fact that correcting him will be embarrassing to him have anything to do with it?

I have wondered the same thing.

I'll be honest, I don't do anything. The fact that no one else does anything makes me think maybe I didn't hear it right and I don't want to risk embarrassing myself.

This past week the person clearly read a kri/k'siv the wrong way 3 times. I thought I noticed it the first time and then was sure the second time. I geared myself up to correct him the 3rd time, but when it come to it there was no way I was going to do it. I think if I had been sitting close to the bimah such that I could correct in an undertone, and the rest of the shul would not hear, I would have done it.

Actually, I believe halachically you're not supposed to correct the guy, but people do it anyway.

I can't think of a reason to correct him, except if you can do it surreptitiously and it's to avoid him being embarrassed by repeating a mistake, whether it's a keri/ kesiv or he mistakenly reads adonoy instead of elohim (which is a type of keri/ kesiv anyway, I guess). Although pronunciation is also a mistake, you can't give a crash course in pronunciation while he's reading, but perhaps you can get him not to mess up two more keri/ kesivs.