Derived terms
My hope is that, once all sections of related and derived terms are templatized, we could have the quick-add stuff which lives at the bottom of translation sections. Personally I like them to be in the boxes even if there is only one, but I understand that not everyone shares that view.
That's overtooling, in my view. Expanding these lists should be very straightforward using wiki markup editing, much more so than expanding the translation tables.
Another motivator is that collapsing these lists increases the amount of highly relevant information which is displayed without scrolling. User experience etc.
In non-English entries, there is often no "highly relevant information" below the derived terms section. As for user experience, having to click to uncollapse a section is a poor user expericence. We collapse translation sections since they eventually get so large.
The default state of a collapsible section is up to the user, so if they want to see what is inside expanded by default they can do that. We have no good data, but I assume that derived and related sections fall very low in the order of information which people are looking for when they are using a dictionary, whereas translations are likely fairly high (after, perhaps, meaning, pronunciation and etymology). The thing about non-templatized list sections is that we don't have a lot of direct control over how they are displayed. If all related and derived sections were in templates we could have a discussion about how best to display them, right now the only option is plain text.
I agree that translations are likely more often sought than DTs and RTs, but you are doing the DT thing in foreign-language entries as well (e.g. budować), which do not have translations. On a slightly related note, I think DTs and RTs should be below translations, as they once were, long time ago. For foreign-language entries, your arguments are very uncompelling, IMHO, and I continue to register my opposition.
If the entry if for a single language, as the one you link, then it certainly does not do much for user experience (although I much prefer the look). Many FL entries are for multiple foreign languages, and in those cases it may raise the visibility of languages beyond the first (see hulda). Our layout leaves a ton to be desired, I think this is a step in the right direction.
The other thing is, I find it peculiar that we should have all DTs collapsed without any public discussion via a run of volume editing simply because you decided that was a good idea. I have spent my energies to prevent these sorts of behaviors in the English Wiktionary, but am not sure I have the energy to deal with it right now.
Since you have not stopped, I created a Beer parlour discussion at Wiktionary:Beer parlour/2016/March#Collapsible derived terms. Maybe I am in the minority; let's see.