Usernames are not bold with Segoe UI on Firefox

**Describe the bug**
Usernames of posts have the same font weight as the contents of the post.
- Site: phanpy.social
- Instance: hachyderm.io

**To Reproduce**
Visit the main feed.

**Expected behavior**
Usernames of posts have a higher font weight than the contents of the post.

**Screenshots**

**Desktop (please complete the following information):**
- OS: Windows 11
- Browser: Firefox v. 123

**Additional context**
The username has the style `font-weight: 500`, and the font resolves to **Segoe UI**.

It looks like Segoe UI has no difference between `font-weight: 400` and `font-weight: 500`, it only gets a different look at `font-weight: 600`. I found a test page that demonstrates this: http://chriskr.github.io/tests/test-segoe-ui.html

Interestingly, in Chrome, the font resolves to **Segoe UI Semibold**, and looks correct: