Describe the bug

While looking into vertical metrics standards for Google Fonts, I realized that my recent PR to Inter was probably not optimal: it's default line height is significantly higher than most comparable fonts.

The root cause of this is that the script I set the vertical metrics with. It sets the winDescent to the lowest y-coordinate in the font. Meanwhile, winAscent is the highest y-coordinate in the font (Å). This helps avoid clashes between lines of text, because winDescent and winAscent are used for the total default line height.

Actually, the MS OpenType spec says:

Some legacy applications use the usWinAscent and usWinDescent values to determine default line spacing. This is strongly discouraged. The sTypo* fields should be used for this purpose.

...but these still seem to be the values used in Sketch & TextEdit. I need to do a bit more research to compare vertical metric values in fonts similar to Inter to know for sure.

However, I believe the design suggestions in this issue are valid, either way.

In Inter, the /ydotbelow glyph has a dot below its descender. This is logical, but seemingly not typical – many other fonts put it to the right of the y. In the case of Inter, it means that the TypoDescender is quite low, and as a result, the default line height is abnormally large.

Here are several fonts set at their default line heights, in Sketch:

And one with Inter's line height reduced:

Expected behavior

I propose two changes:

1. The ydotbelow dot is moved up and to the right, as in comparable fonts
2. The commaaccentbelow is made slightly more compact (less critical, but still useful). It is the second-lowest object in the font, and significantly bigger than commaaccents from related designs.

Environment

• OS: macOS 10.14, Core Text
• App that renders the font: Sketch, TextEdit, etc
• Version of font: Version 3.004;git-8321f7c65

Additional context
I wanted to note down my research in an issue, and (unless something big comes up) I'll change these things tomorrow, adjust the vertical metrics again, and submit another PR. Vertical metrics are some of the more important things to really get right before we publish to Google Fonts, because it will obviously make a very big difference to people's layouts if these change after the font is implemented in websites, etc.