That would have been fairly useless.

From my perspective, the dilemma you face is that you could say "a lot of people think that expressing opinions that disagree with theirs constitutes aggression", which would be non-content-free but ridiculous, or you could say "some people think that some expressions of opinion constitute aggression", which would be true but almost content-free; I'm having trouble figuring out what you could have meant that would be contentful but in any way plausible.

it seems to me that [aggression] means [to gjm[ just being impolite.

They're closely related. Aggression is (among other things) one variety of impoliteness. (In ordinary social contexts. If you're facing an opponent in a boxing ring, aggression isn't impolite.)

Alice [...] Bob [...] Charlie [...] Duncan

Is A listening to B, C, and D? Or are they saying this in some venue that records what they say, where A might come across it later? Or perhaps not A but some of her friends and family?

If not, I don't think I'd call their comments aggressive at all. So let's suppose B, C, and D know that their comments are likely to be heard by A. Then yeah, all else being equal I would say B<C<D in aggression.

I find it strange that you pay so much attention to the form and relatively little to the content.

I find it strange that you say that, for two reasons. Firstly, there most certainly is a difference in content between what B, C, and D are saying. (And, referring back to the original discussion, between "Transgender people suffer from gender identity disorder, which I classify as a mental illness" and "Transgender people are delusional and hallucinating".) Just as there is a difference between "Lumifer has some unusual political opinions" and "Lumifer is a fascist". (Note for the avoidance of doubt: I do not think you are a fascist and have no idea how usual your political opinions are.)

Secondly, there's a lot of information in the form. The difference between "Joe has difficulty understanding some things" and "Joe is a fucking moron" is largely one of form, and mostly what it indicates is hostility. Similarly, it's easy enough to see how someone could express opinions about transgender people quite similar to VoiceOfRa's with a much less hostile tone. That would (as I use the word) be less aggressive. It would be less likely to make any trans people reading LW feel attacked; less likely to make them expect that if their trans-ness became known they'd be met with hostility and contempt.

LW as a whole [...] or your karma [...]?

I tried to make it clear that I'm well aware of the difference (acknowledging that my judgement of my own comments is far from impartial; citing what happens to other leftish-leaning comments; "part of what I mean". Did I really fail so badly? (Or: did I succeed but do you think I'm disastrously self-deceiving or something?)

Think of LW as a place of refuge

See, this is why I find it odd that you say LW doesn't lean right. Because providing a "safe place" for neoreactionaries would, I think, generally be regarded -- even by people who consider themselves right-wing -- as evidence of either (1) rightishness or (2) fanatical refusal to make anyone unwelcome on account of their sociopolitical views. And if you think it's #2, then I invite you to imagine the roasting that the residents of that "wrong Tumblr neighbourhood" would get if they turned up on LW.