Going to comment on each of the topics separately, as William_Bur has done:

1) I pretty much agree with the point that objectifying is fine if we objectified everyone equally - if androsexual commenters talked about unattractive men the same way gynosexual commenters talked about unattractive women, say. However statistically speaking that's not going to happen, just because there's a much higher proportion of gynosexuals on this site than androsexuals. As the current gender proportions stand, it's going to look like men are the in-group and women are the out-group, even if people objectified the objects of their desires to the same extent.

As such, I think if we fixed the other two problems and actually attracted more women to this site (more gay and bisexual male conversations about getting guys might also work, though I'm not really aware of much of a LGBT presence on LW), this one is going to fix itself. (Assuming we have sensible community norms like "mentally flip the genders in your post before you post to check this is normal objectifying rather than super-offensive objectifying", which I think we can do.)

2) I don't have much to say about this one. For me the most likely hypothesis is that people are bad at hearing evidence that don't agree with their current prejudices and vice versa, so if we already have a community that agrees with unsupported theories about evopsych (for whatever reason) then it's going to post more studies about it and agree with them.

I feel similarly when people talk about paleo diets, actually. I personally prefer to just not publicly discuss topics where I feel the evidence is insufficient.

3) Anecdotal evidence suggests to me that female geeks tend to notice/focus on niceness and social codes more than male geeks, though both in turn focus on it less than non-geeks (though in non-geeks men and women often have different social codes). There are many hypotheses as to why this could be if this were true, but I don't know well enough to speculate. There are also a lot more male geeks than female geeks. If this observation is true across the population then a website ostensibly aimed at geeks will end up with a lower level of niceness than the female geeks would like.

I'm going to be objectifying here and suggest that not being nice enough is a typical trait of low-status geeky males who've not learned the value of social codes, and that the only reason this is a problem is because we don't have enough high-status men to enforce sensible standards on it (I would normally put a ";)" as the punctuation of this sentence, but since elsewhere someone mentioned emoticons being objected to I'll verbally disclaim that the previous sentence is intended with a light-hearted tone). Politeness and compliments are not a waste of time in the same way that dressing nicely is not a waste of time - if people like you more, they're more likely to take what you say seriously. Similarly, understanding how the tone of your voice (or typed comment) comes across is an important life skill that people should put effort into learning if they don't know how to do it.

Alternative hypothesis if people believe that they do know how to be nice, they just don't do it on LW: do you act differently with all-male groups compared to mixed groups in real life? If you do, you should post as if you are in the latter if you wish LW to become the latter.

ETA: Data-gathering to calibrate the accuracy of my own hypotheses below.

Questions for men:

Are you more or less friendly on LW than you are in real life?

Do you behave differently in mixed groups compared to male only groups?

Questions for women:

Is the tone on LW more or less friendly than in male-dominated groups you are part of in real life?