Here's a thought:
Write a program to log every users username. Make it so that it runs automatically. Then write a new program that uses the the LFS World member search function. Use the scale that someone suggested. You can then use that to weed out the invalid usernames. After you weed out the ,erm, weeds, you can then worry about the others. Write a program that will search for things in groups and ID found terms. Such as: "Search for <"Username, S1", "Username, S2", "Username, Demo">" and assign a value to each item. For instance, If the <Username, S1> is found, have it print "true S1." And if <Username, S2> is found, print "true S2." and if <Username, Demo> is found, print "true Demo." If no terms are satisfied, then print "No Such User."
Anyways I hope that made sense, I have just been introduced into programming so some of my ideas may be flawed.