To me it doesn't seem that bad in this particular use case. Text is still perfectly readable and acceptable to me for its purpose in this context. Heck, you enlarged that image just to emphasize the visual artifacts around the characters. And at that, compression settings more tailored to this purpose could improve upon that. GyfCat uses "well-rounded" settings for their more general use case of converting any/all GIFs to video. Since this is for a very specific use case -- terminal screencasts -- you could probably improve on visual quality while maintaining improved (smaller) file size by tweaking the compression settings.