"Cloak" mode doesn't cloak posts in the middle of a thread

**Describe the bug**
A clear and concise description of what the bug is.
- Which site: dev.phanpy.social and phanpy.social
- Which site version: dev.phanpy.social 2024.06.29.e6e884f / phanpy.social 2024.07.01.5e9165b
- Which instance: social.alexwlchan.net, which is hosted by Masto.host

**To Reproduce**
I can reproduce this reliably, but only with a single thread in my timeline: https://social.polotek.net/@polotek/112729542936769413

It reproduces on both instances, if I turn off/on the cloaking.

Possibly notably, this is the only thread that is visible when I scroll to the top of my timeline. If I scroll down, mid-thread posts from other threads are cloaked correctly.

**Expected behavior**
All the posts should be cloaked.

**Screenshots**
Some of the posts are visible:

**Desktop (please complete the following information):**
- OS: macOS Sonoma
- Browser: Safari
- Version: 17.5

**Additional context**
This may be related to #121, which looks like a similar issue.