There is no limit on the size of one's personal ignore list.
People should not speculate about why a post or thread doesn't get a lot of replies. It usually has nothing to do with a person's ignore list and is just a result of people either not seeing the thread or not having anything they think will add to it.
People also shouldn't speculate about why another member is on an ignore list. It is a self-help tool we provide to all members to ensure they have a safe experience here. Speculating about other members and their motivations is not in keeping with our community guidelines.