Not to be pedantic, but as mentioned elsewhere every tip here (sans the dropdown on hover one) is in the documentation itself.
I'm really not trying to poo-poo the article but you could pluck 10 random things from Bootstrap's relatively simple documentation and have the same thing.
Maybe if it were titled "cool things in Bootstrap" instead of being presented as "tricks."
"I'd call a trick something that is not part of the documentation core .." I'd call this particular definition a pedantic, artificial nitpick invented soley for the purpose of picking nits in the post.
If on the other hand you use a conventional definition of trick, "a clever or particular way of doing something", then the post is indeed about a set of tricks.
The funny thing about your newly defined "trick" is that it would be foolish to rely on such undocumented behavior not changing on the next minor update. :)
Well the same applies to this definition of "trick" so I'm not sure that's a particularly damning point.
Either way, I didn't say such "tricks" are without peril - surely a number of jQuery "tricks," even those that were eventually canonized, have been broken over the years as the library updates.
What exactly is a "trick" then? I would argue that they're useful bits of functionality that a group of people might not know. For instance, if I post "math tips and tricks" to my facebook followers they'd be like "ooh, nice tips" but if I post them on a /r/mathematics I'd be told "they aren't tricks, that's just the way math works". I think you're just basically saying "I know this already so everyone else should too".
Math "tricks" are usually computational in nature (and so not particularly "mathematics") and while it might be obvious how they work to a mathematician, they are unlikely something the mathematician would expect to find in a textbook. (I was a math major for a few years in college, and have a ton of friends who still do research in and around mathematics today.)
I'm really not trying to poo-poo the article but you could pluck 10 random things from Bootstrap's relatively simple documentation and have the same thing.
Maybe if it were titled "cool things in Bootstrap" instead of being presented as "tricks."