This is one of a long line of people arguing for or against what's essentially Sapir-Worf—people have been strongly divided on it for a long time. I'm surprised to see that something like this article is getting attention, though. I figured that at this late date you'd have to say something much more compelling/nuanced to be considered as adding to the subject.

Where I've seen this discussed, most people seem to agree with you - that they don't personally feel any difference.

However, I personally feel a huge difference in how I perceive the world - in the three-ish languages I know, but I also feel some differences in regional variations of British English.

It's for this reason I feel fascinated by language and saddened that people seem to be converging on English as a lingua franca.

This was my first thought, and I was surprised they didn't mention it - perhaps simply because it's allegedly a controversial subject. Regards the controversy - as with many others unburdened by formal training in the area, much of Sapir-Worf 'makes sense to me'.

One area that I don't see discussed so much is variations of fluency within a language, and how that shapes the way a person can internally model, and obviously describe and influence to others, both physical objects as well as more nebulous constructs. Again, anecdotally, I've seen a strong correlation between skills with former and latter, though obviously it's not a simple, one-way, causal relationship.

I vaguely recall an HN story last year, about a school in NY (US), emphasising rigously expanding the students' vocabulary & language skills based on this premise. Might have been the University Prep in Brooklyn, but what I can find of that one now seem to emphasis maths & physics above English.