The user-agent string for Opera 15 Next (the first preview of the new Webkit^H^H^H^H^H^HBlink-based browser) is 140 characters long. You can Tweet it, but there’s no room for even a 1-letter comment. (Note also the sheer number of engine/browser names that aren’t accurate, but are included for backward compatibility with browser sniffing websites).
“Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.20 Safari/537.36 OPR/15.0.1147.18 (Edition Next)”
Comment from Brion:
UA sniffing has to end… it’s also soooooo easy to do lazy regexes that count Firefox 20 as Firefox 2, etc. 😛
I think the only still-required UA sniffing we’re doing for Wikipedia is trying to detect mobile devices… lots of weird entries for older devices, then simple checks for modern ones. Sigh.