Bold Font Size Inconsistencies in Folder Lists with Slack

I am unable to modify the bold font used for folder lists, which is particularly noticeable when using Slack with eM Client. The default font size is too small for my preference. When I attempt to change the font to something larger, read messages display correctly, but unread (bold) messages still appear in the original font and size. I am currently using version 10.0.3530.0.