Environment:
Firefox 99.0 (64-bit) / Linux

WTR:

1. Open new tab
2. In developer tools set up throttling to Regular 3g (easy way to reproduce, but I met the bug originally using regular internet)
3. Open https://remark42.com/demo/
4. Start pressing End button immediately until reaching the first comment

Result:
Several posts are below footer, one of the posts is cropped

Excepted result:
Images doesn't brake markup after loading