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Bold Chinese that stays readable

Bold Chinese should not smudge into a blob. The same words, the same phone, before and after.

One look is enough

Terminals lean on bold everywhere: command output, a grep match, your prompt, the tmux status line, the headings in a man page. For Latin letters that is fine. For Chinese it is not — the strokes are already packed close together, and thickening them fills the gaps between them until the character is one dark blob.

Below are two crops of the same Traditional Chinese line, same phone, same size. The only difference is how bold is drawn.

BEFORE Terminal capture: a line of regular-weight Traditional Chinese, and below it the same line in bold, with the strokes merged together.
Before: bold was faked by drawing the character twice, slightly apart. On a dense character the gaps inside 繁 / 體 / 測 fill in and only a blob is left — the regular line above it is easier to read.
AFTER Terminal capture: a line of regular-weight Traditional Chinese, and below it the same line in bold, with every stroke still separate.
Now: bold comes from the bold shapes the system Chinese font already contains. It is heavier where it should be, the gaps inside each character survive, and you can read it at a glance.
Why it is worth fixing

In a terminal bold carries meaning: this matters, this is the match, this is a heading. If bold is the hardest thing on screen to read, that emphasis has been spent for nothing — you stop and work out what the words are instead.

For anyone working in Chinese this is a daily occurrence: any bold Chinese in a log line, a prompt or a script’s output came out as that blob. So it is not a question of nicer typography, it is whether you can keep reading.

Terminal capture: Simplified and Traditional Chinese, each with a regular and a bold line, plus a red bold and regular pair.
Simplified, Traditional, and a coloured pair: in each one the upper line is regular and the lower is bold. The weights are clearly different, and colour costs nothing in clarity.
Where it applies

It follows the Chinese text in your terminal; there is nothing to turn on. Two honest boundaries, better stated than glossed over.

Japanese and Korean are unchanged for now

The system Chinese font carries no Korean, and many Han characters are written differently in Japanese — borrowing the Chinese bold would show a Japanese reader shapes that are simply wrong. So Japanese and Korean keep the previous path: the shapes are right, the bold is still synthesized.

Changing the terminal font does not change this

Pick any terminal font you like for letters and digits; Chinese is always drawn by the system Chinese font. If your chosen font ships a bold of its own, Latin bold uses those shapes too; if it does not, Latin bold stays as it was and Chinese is legible either way.