TracksApp/tracks — comment on commit f7875d57af8e0c4c59d2770f6272c6a0e244cd69
File:  line 0
By lukemelia:

My rule of thumb is to make experiences better for modern browsers using web standards when it doesn't make experiences worse for users stuck on older browsers. This commit adds rounded corners for capable browsers and does nothing for older browsers.

You're right that not all features are like this one, though, and the project should decide what browsers are supported on desktop and mobile.