Yeah because that's all people do with achievements. Can we knock it off with the dismissive attitude?
I mean, I dunno if I'd go so far as to be dismissive about them or if I'd describe them as how that user did but let's call it for what they are, and that it is indeed for showing off. On PS4, your trophy rank is front and centre of your profile, you are notified (I'm pretty sure by default) what trophies your friends have earned in the What's New section and certain games have their leaderboards/achievements vs your friends viewable on the main menu, and on Xbox there is a leaderboard for who has amassed the most Gamerscore per month.
You don't need to be offended by just seeing these for what they are, they're just system wide frivolous ways to physiologically increase player retention and competition between friends, and he with the most shiny gold and platinum trophies is king.
Like I know I didn't kill 20 cows in The Witcher 3 because I gain satisfaction from doing it, nor because it was in the spirt of the game or the character I was role playing as, or even because it was an actual mission or sidequest in the game. I did it because there was a shiny trophy that would be easily MINE ALL MINE if I spent 2 minutes doing it... and that is the mental affect it has when it gets to you. Like when I'm on my deathbed I may remember that I spent 2 minutes of my limited time alive slaughtering digital cows just to get a digital bronze trophy.
It's laughable really when you think about it.
I like to think I don't care about them on an actual mental level, if I logged in tomorrow and they were all gone I'd not miss them, but even I feel a sense of smugness when I have a particular gold/silver trophy my friends don't and I know they know you know?
It's basic human instinct and they're developed in such a way to play into that.