I'm pretty sure that's how most, if not all, instant messaging services worked 20 years ago... Was a feature, not a bug. The whole idea of sending an instant message. If you wanted to send a non-instant message, you'd send an email instead.
My focus was not so much on pixel perfect, but instead on creating something that would also work and look aesthetically pleasing on modern systems, like with higher DPI monitors and such. So one of the the things I did was to recreate all the icons and symbols in SVG.
I tried posting it as a Show HN when I added XP and Mac OS 9, but it didn't get much attention. Maybe the title of the project isn't as catchy.