@Jhernandez Some of the caution comes from "Segoe UI" also becoming default on anything Windows Vista+ besides Windows Phone. And if we gonna go for other font choices on desktop aside of Mac, we should be very sure what we're going for. Also adding this to Windows and not caring about other free operating systems doesn't make sense in my opinion.
Additionally as too often, the situation on Windows Phone is not fully clear from MSDN. This article lists "Segoe WP" before "Segoe UI" for Windows Phone 8.

@01tonythomas @Florian @matmarex What's missing here?

All our 'x' icons are in the upper right corner in normal dialogs and cards. From the screenshot above, it seems that the image increased, so would there be space to put the translation language filter below?

Those two resources explain which font in the stack is used on which platform as default:

Note to myself: After turning to padding we have now mostly only one property to control width/height and distances, but variables number might get a bit overwhelming on first sight:

• We could mix line-height with padding to address/decrease the top/bottom variety, on single-line widgets
• There's also one occurrence where missing box-sizing results in one pixel difference and to extra vars.

@matmarex We should definitely avoid vertical scrolling of tabs.
Wrapping sounds like the minimum compromise, although it's, especially with a large number of tabs, also not a good user experience, as users might for example loose context where they are.

@Dvorapa, thanks for the inputs. There are a few things to consider on top, like if the representation of the sections (“Skin”, “Reading preferences”…) all with a border and padding instead of bigger font-size and margin-top only on the heading were to gain us a good amount of vertical space.

I agree that renaming in general would just shift the confusion to another place. From my point of view, it should alter the title depending on where the click was initiated, therefore the title “when inserting media”.
When the initial click was on the “Insert Media” button in the toolbar, title should change. When the initial click was on an already inserted image it can stay “Media settings” or a better default name for the dialog.

Toolbar candidates for removal on smaller viewports:

• “Cite”
• “Special character”
• “Help”

As of 14 Sep 2017 all toolbar tools and dropdowns in VE have tooltips applied.

This seems all a bit mish-mashed.

Here's a heavy-load test case not even close to reality as we currently don't have anything bigger than SVGs under few KBs (haven't found anything above 2 KBs in short search) as data: URIs:
https://codepen.io/Volker_E/full/BwyQwo/

As the article states:

but only ' is allowed in a URL.

In order to provide users a better experience, resulting in higher acceptance in that change it would need some extra per-extension CSS:

• don't provide two primary action buttons, rather a solution as proposed in T28256#3234020
• adding margin-bottom: .5em` to .mw-fr-ratingselects || .fr-ratingoptions
• vertical align the “Comment:” label

Related task: T100706: Revamp anti-spamming strategies and improve UX

@Quiddity Not sure if this is still an issue with our work on aligning core to overhauled WCAG level AA conforming colors in core and therein also in shared.css.

Well, the reason is simple: The paths are different on the 24x24 px canvas:
Clip/unClip is 14x18 px versus trash/unTrash is 12x15 px versus article being 13x16 px.
As Design team is currently going through updating all icons and harmonize paths sizing with canvas across our icon set, I'd put this on stalled before introducing special treatment that is just around several weeks.

@Capt_Swing If you're referring to the two points in the task description, my plan is to give the CSS/JS highlight another shot.

Base vars follow-up at https://gerrit.wikimedia.org/r/#/c/377036/