I got that from other people as well. My rationale is that, once clicked, the explanation now becomes part of the text, so why would you want to hide it? You read it and move on, so there's no sense for the link staying there and cluttering the text.
If there's significant demand, though, I can certainly make it an option. It sounds like leaving expanded stuff expanded bothers some people's OCD, which I can certainly understand :)
I'm in agreeance with you here. I like how it becomes part of the text. It's not like your adding paragraphs and that make the page unruly longer and cause you to lose you place. I say leave it as is. I thought it was really nifty when I saw it too. :)
Yep, exactly. The idea is that you'd write the sentences being part of the text (as you would normally), and then just hide them behind an expounder link. You just need to take some minimal care for the next sentence to make sense, but other than that, it produces great results. For example, I like the effect it has on the "NodeMCU" link in the article, which you can click if you're unfamiliar with it and you'll get a fitting explanation.
Another section I like is the "rather optional", which explains the rationale for people who may not be aware of it. An author should not fall into the trap of hiding information that's not strictly relevant to the link, though, because then they trap the user into a "okay I need to expand all the links because who knows where the author has hidden useful information" mentality, which kills its usefulness.
will be interesting to see how well they manage to lock down the rest of the system