Offering usernames will allow people to stop giving out their phone number —a sensitive piece of information— in order to connect with others on the messaging app.
Gifs work if you add them from your PC rather than from an URL. Download it, pull it into chat, gift works. It's not as easy as it should be, but at least it has a workaround
My main problem is that they wouldn't allow registration without having a smartphone first. At first I used signal-cli, which was inconvenient because there was no message history even. Now I use it in Waydroid, but why should one bother like that? And last time I tried it, the only way to bind a different device was by scanning a QR, which is not doable by Waydroid and iirc kinda hard in a VM.