In my experience it's nobody specific, but we all do put a lot of stock into very niche things to justify our lore theory as being the "correct" one when we really should just be considering this as a chat around the fire.
I am guilty of this as well- it's important to talk about your ideas, but to be very comfortable with the understanding that it's not gospel..and also accept the opposite: Just because someone says something in conflict with your ideas, doesn't mean they are attacking your ideas, nor that they are set in that opinion. Often it's just spitting ideas.
I would offer people (myself included) a simple mantra: "I have nothing of value to add to this line of thought", and then, just post nothing. No need to get in a last word, even if it's just a snippy "Well we just have to agree to disagree".
I would also offer that it might need to be said: This is text, and text is often read incorrectly to be aggressive or negative. As you said, assume people are writing in good faith and if you feel someone's digging at you.. assume they're probably not.