1. When a mapper is learning to map, and indeed learning to make a good map, they shouldn't publicly release a map until they've made a good quality map. When they make test maps to learn mapping, or to try to make a proper map, those maps should be kept on their hard drive, or perhaps privately released to acquaintances and more experienced mappers for testing and feedback, until they manage to make a good map - the good map is the first one they should publicly release.2. Being a first time mapper is no excuse whatsoever for releasing a bad quality map. Some mappers mistakenly think it is, and try to make such excuses in their texts - sorry, but that excuse simply isn't acceptable. Firstly, the reason above, bad quality maps that one makes while learning to map should be kept on the hard drive until a good quality map is achieved. Secondly, there are plenty of people, from all genres of mapping, who have released good quality maps as their first released maps, some of these have indeed been excellent maps.
Is the entire Quake modding scene this hostile to newbies or is it just this one dude?
This attitude may have made sense back in 2001 when Quake was only about five years old and you could presumably get your friends to check out your first attempts at levels when you hauled your computers into one room for bi-weekly LAN party but when we're talking about a thirty-year-old game I somehow suspect most of your friends are gonna be playing something slightly newer most of the time.