Read receipts have regressed visually

[robintown]

Steps to reproduce

1. View any high-traffic room
2. Look at the read receipts

Outcome

What did you expect?

Read receipts should be in groups of 3, stacked on top of each other from left to right, and there should be no gaps in the layout.

What happened instead?

Visually broken read receipts appearing in unevenly spaced groups of 4:

Read receipts stacked in an unusual order:

Operating system

NixOS unstable

Browser information

Firefox 108.0.2

URL for webapp

develop.element.io

Application version

Element version: 50f2b53-react-e9d723269f2e-js-4f918f684e9d Olm version: 3.2.12

Homeserver

Synapse 1.75.0

Will you send logs?

No

[t3chguy]

Believed to be regressed by matrix-org/matrix-react-sdk@a8aa4de