Comb filtering happens when a sound mixes with its own reflection, or a signal is mixed with a delayed version of itself. It can sound subtly bad; it can sound absolutely dreadful. The one thing it never sounds is good. If you watch the video and hear the demos then you'll be prepared for the worst.
Great home recording starts with a great home recording studio. It doesn't need to be expensive if you know how to select the right equipment for your needs.