So I’ve been wanting to make this post for a while now. I finally sat down and did it.
I think Dave’s up to something (not going to guess at what, but something more than the “platonic connection” MSPA wiki says it is) with Terezi, and my theory comes from his behavior when talking about the subject.
From the start of Homestuck, there’s been a few instances where Dave’s talked to others, both in joke and serious situations about romantic advances with regards to various characters.
In all of these cases

he never really attempts to shut down the conversation

instead he ironically or otherwise leads it on, exaggerates the circumstances he’s accused of

plays the big casanova role and everything, never denies anythin’ at all even though i’m sure at least some of these advances he didn’t take seriously

plays the whole hot pimp facade, like look, even with regards to terezi:

nope, no denial whatsoever - even brings up the hitting on thing again:

But let’s fast-forward a year. To the time of A6I2. Dave and Terezi have been on the meteor for a year, hanging out, feeling “something” of some sort for each other. Here’s why that “something” - at least from Dave’s perspective, is more than just friends.
Look at his reactions to being questioned about a romantic relationship with Terezi now.

Notice anything different. Like, conversation shut-downs.

Or downplays rather than exaggerations of the activity.
Or heck, even refusing to let Karkat draw something Karkat had drawn before and Dave had humored before (see above log):

Woah, complete-180, am I right? Suddenly he’s playing total “shut the fuck up” mode when spoken to about a relationship with another character in a romantic context, something he’s never done before.
But what the heck’s the difference? Okay I’ll tell you.
There really is only one thing: these accusations aren’t like the old ones, which were jokes and held no merit - why would they hold merit, those were all accusations about connections between Dave and individuals he hadn’t met before, had only exchanged a few logs with, didn’t have such feelings for, saw as friends or at the very least, hadn’t spent a whole year with. These A6I2 accusations regarding Terezi had some bearing on the truth.
As most of you would know, Dave leads a life which is essentially a facade. He’ll make things up - or lead lies on - exaggerates it in the name of “irony” to create his “pimpdog hustledaddy coolkid” persona, or any other coolkid persona for that matter. But when he’s questioned on something personal, or at least which poses a threat to the whole persona, he gets his insecurities on about it - shuts down the conversations -
like when he’s being asked to reveal his eyes

or, at least at first, admitting the whole being disturbed by puppets thing

it’s all just “shut up” “fuck you”
why? because admitting these things are a threat to his steely facade.
Yet they wouldn’t be a problem if they weren’t truthful, weren’t serious. he’d lead them on, like he did with all the joke/unserious romantic advances, right?
Something’s different here.
Something’s truthful, and he doesn’t want to admit it. For some reason, speaking up about the accusation that he’s doing something romantic, intimate with Terezi is a threat to his facade. Maybe he thinks one-on-one sweet romance (not the pimp stuff) and makeouts or whatever the hell they’re doing isn’t a thing for coolkids, I don’t know what it is, I don’t have enough to guess at it. But if you notice the pattern in how Dave responds to conversations I find that that there’s something here to say that he won’t talk simply because he’s embarrassed of the truth, but he can’t deny it cause well…it’s true. Hence shut up shut up shut up. Don’t want to talk about it.
And that’s all there is to that. Hope y’all see it too.
/end rant