Message spacing for sequential messages
This is a feature in Apple's iMessage that I didn't realize was useful until I started using Briar Android and Desktop frequently. For sequential messages that are sent within ~1 minute of each other, by the same contact, Apple changes the spacing to about 1-2px. The result is that message bubbles sent in the same window are grouped together and are easier to read as a collective group.
Not sure how hard this would be to implement on the back end, but there's a chance compose makes it fairly easy.