I don't remember who was the first person to write a comment in another language than French on that thread, but I remember for sure that that comment was in Dutch.
About flexing muscles and such, my friends and I fight (verbally) every day to see who's better. It's mainly a male thing, I think. But we enjoy our little fights. We've come to the conclusion that when we're 80 years old, and in a wheelchair, we'll still race down the halls to the retirement home's cafeteria.
However, regarding the thread you mention, I wasn't even fighting. I recall having made one silly comment in Dutch in response to either you or your husband, asking where the nearest coffee shop was, after using a translation application as I don't know any Dutch at all. It was meant as a joke, not as a muscle-flexing bout.
And I also recall having tried to decipher the arabic comment, as a challenge, not as a show-off. And even then I added a joke about jihad.
So perhaps there is no need for hasty conclusions about people. I'm talking for me here, perhaps others feel the same.
I thus think that multi-lingual threads are a good opportunity for people to give it a try ... if I didn't try, I'd stick to English and French, the only two languages in which I don't have to think before writing.
Fortunately, I like thinking, and as a result, I like writing in moderate Spanish, poor Russian, obscene Sinhala, or fake Dutch ... and this brings me one step closer to the Spaniards, the Russians, the Sinhalese and the Dutch ... and I like that.
Write in French and I'll find it great that you're trying. I won't even begin to consider that you're showing off or anything of the sort. And even if you were, I wouldn't give a damn. That's valid for me ... but since we're all different, you're entitled to disagree ... but please, if you start cursing, do it in Dutch so I can learn a few swear words on the way ;))