I think it would be a pretty rare squatter who'd turn down say $300 free and clear for an obscure domain, provided you don't clue him in to your interest. As one of the other commenters said, just approach it casually and don't clue him into the fact that you want this domain badly enough to post on HN about it.

Being friendly always helps; don't seem annoyed by the fact that he's squatting, don't say stuff like, "well, you're not using it anyway", etc.

That's point #1. The second point is: why do you really need the .COM anyway? Do you anticipate a lot of people typing your domain in directly? Won't they use Google? The competitive advantage of .COM vs. .XYZ is nothing like it used to be IMO. Take 4chan.org and 4chan.com as a colorful example.

The bottom line is that if your product is useful and your website is indexed, people will find your site. They're not going to hit the parked page and think your site doesn't exist. I mean, if you were selling lolcats it would be one thing but for an SaaS product with tech-savvy users?

Also, don't go through the automated "make an offer on this domain" process that some registrars (eg Godaddy) have. In my experience that increases the perceived value of the domain, because the guy on the receiving end gets a nice colorful email, etc, "ooh! somebody's interested in your domain". Just send a short, boring three-liner to him directly.