That's weird. My friends would be ecstatic for us if we had a mortgage burning party. But I guess my friends aren't typical. We have one set of close friends who made it their goal to have a paid-off house before they were 30, and we were there to celebrate with them when they succeeded. I have another close friend who lives in a bus that she paid $7K for and renovated. And another couple who are one track to retire by 40 (we discovered MMM independently and were thrilled to learn that we were both working to FIRE). My boss is also an MMM-reader and he's recommended it to all of my co-workers (most of them are reasonable with their money, but not necessarily frugal). Yeah, now that I think about, my friends aren't typical at all.
At that point in time, my wife and I were graduate students/pseudo professional athletes (ok, with the benefit of hindsight: wannabe professional athletes). Our friends were mostly penniless graduate students and penniless mountain bike racers who lived in shared student-ghetto rental houses.
The idea of *having* a mortgage or owning a home was pretty foreign to the whole crowd. So yes, the initial reaction when we mentioned the mortgage-burning party was disbelief followed by jealousy. Now, nobody would have outright been a jerk about it or immediately terminated the friendship or anything. But it became clear to us pretty fast that it would harm our relationships with most of our friends to, so to speak, rub their faces in our financial success.
We now live around a ton of really rich people (or, at least, people who earn a ton of money - doctors, IT pros, etc) and it's still awkward because we're the couple that are both volunteering at school and coaching sports teams and out in the middle of the day mountain biking or skiing while all our neighbors are working 60 hours a week. Everyone around here assumes we're trustfunders but since we have basically zero nice possessions they also think maybe we're dirt poor.
I think if you really are financially literate and have FIRE as a goal/have achieved FIRE, you are always going to deal with some level of awkwardness when it comes to discussing money with your friends/family/neighbors. I mean, our neighbors who work their asses off and never see their kids have 3 BMWs in the garage. We ride our bikes and own one car worth maybe $1000 if you're extremely generous. Things get awkward fast when lifestyles and financial choices are that different, but for me it makes more sense to just not talk about money (this includes throwing a party involving paying off a mortgage) in situations where it will cause problems.
-W