List of cancerous prefixes


 * pls
 * catpls
 * pls pls
 * i cast
 * ​ (U+200B / zero width space)
 * zeit!
 * _
 * __
 * pls pls
 * i cast
 * ​ (U+200B / zero width space)
 * zeit!
 * _
 * __
 * _
 * __
 * _
 * __
 * _
 * __
 * _
 * __
 * __

The worst case of cancerous prefix is broken command handler which accepts any prefix. That's gross and very likely causes spam so any bots which are doing that are instantly muted.