Windows – Skype font size too big after changing it on HiDPI display

I'm using Skype 7.13¹. I'm using Windows 10, refreshed two days ago, meaning I haven't touched compatibility settings or anything I could've forgotten about. I have a HiDPI display, set to 225% scaling.

Because Skype's font sizing decisions are inscrutable², I wanted to adjust my font size for the messages at least. I bumped it up to about 16pt, and the fonts showed up gigantic, so I changed it to the smallest size available – 8 pt – and they're still huge.

Is there any way to meaningfully adjust font size in Skype, or is this a known bug in Skype and all I can do is wait?

_{1. …point something, see screenshot below.}
^{2. Why are half the UI elements 1-2 pt smaller than the standard systemwide font size?!}