This is a somewhat strange word order to me, I would say "Is múinteoir é an fear". Does it matter at all, or is this another regional thing?
Múinteoir is ea an fear, puts more emphasis on múinteoir. That is it is a version of "Is múinteoir é an fear" with more emphasis on "múinteoir".
In the South however it is the normal version of the sentence and "Is múinteoir é an fear" isn't really said.
Exactly. This is just a way to stress that he's a teacher. It'd be like "He's a teacher", with extra stress on teacher, in English.
This looks very wrong to me. It's masculin so shouldn't it be é instead of ea nd sentance start with verb? Like "is é múinteoir é an fear"?
This sentence structure emphasizes múinteoir. The analogous sentence structure without emphasis would be Is múinteoir é an fear. (and in Ulster Irish, the é could be omitted).
We do it in English, too. "Who's at the door?" "It's a charity collector". Or in French. "C'est une femme" (It's a woman). Or even with plurals. "Who's making that noise?" "Oh, it's just kids playing.""
I hate when we get sentences like this. Why haven't we seen sentences that didn't start with the verb before? I looked at this, thought of several ways this sentence could go but had no idea which one because I had never seen a sentence like it. I have never seen the "ea" except in the "It is" (or whatever) exercise. I wonder if there will be any more of these so we can get used to them?