Originally reported in iTXTech/Genisys#1188 "deop PotterHarry98" will remove "potterharry98" from the ops.txt but not "PotterHarry98". Operator permissions are checked using "Config->exists()" with "lowercase=true", which will result in a match: https://github.com/pmmp/PocketMine-MP/blob/22bb1ce8e03dba57173debf0415390511d68e045/src/utils/Config.php#L449 This means that it's possible to make yourself impossible to de-op (using commands) by adding your name to ops.txt with uppercase letters.