Using /flush when there is info in the user list, it wont flush the specified levels.
Example:
User List:
20:petunia 1066938171
6:not^sweetie 1066938677
10:JIMBOB 1066946241 quitting
10:blx^bbs 1066941845 quitting
5:Pandeh-Ultrin 1066939950 leaving #sexychat!
10:Luanna 1066890600
7:ADeepThought 1066940470 quitting
8:sexybaby 1066940782 getting kicked from #sexychat!
/flush 5,6,7,8 will return:
* No nicks needed to be flushed