What are thresholds?
Your “threshold” is the minimum score that a comment needs to have if it is to be displayed to you. Comments are scored from -1 to 5, and you can set your threshold at any score within that range. So, for example, if you set your threshold at 2, only comments with scores of 2 or above would be displayed. Setting your threshold at -1 will display all comments. 0 is almost all comments. 1 filters out most Anonymous Cowards, and so on. Higher threshold settings reduce the number of comments you see, but (in theory, anyway) the quality of the posts you do see increases.