The sidebar and entries list have less right and left padding.

This means smaller withe margins to each side in smartphones.
Less wasted whitespace in entry-open links.
Cleaning up of the entry content markup.
The reduction in padding introduced in 1760bb31e8db27bed61c29d576f25c5368894c7d now happens only in xs and sm viewports.

This maximizes used space in small screens, while giving the layout enough breathing space in bigger ones.
The reduction in padding in 02ff2923d6f3fa374ea4abf3774b8654881adc61 only happens for md and lg screens (screen widths above 992px).

This maximizes useful screen space in smartphones and tablets, while giving enough space to the layout in larger screens.
Corrected CSS comment (actual behavior was just the opposite to what the comment said).
Add extra padding to entry contents only in medium and large screens.

This optimizes reading space across different viewport widths.