The mod, specifically IRCConnectionImpl.java and possibly other components, only checks for @ (op) and + (voice) when it should also check for ~ (founder), & (superop), and % (halfop)

For future proofing you should check for any prefix specified in PREFIX="" on 005 RPL_ISUPPORT

Sample

:labyrinth.ga.us.irchighway.net 005 DiceBot SAFELIST SILENCE KNOCK FNC WATCH=128 CHANLIMIT=#&:30 MAXLIST=be:60 NICKLEN=30 TOPICLEN=307 KICKLEN=307 CHANNELLEN=32 :are available on this server
:labyrinth.ga.us.irchighway.net 005 DiceBot EXCEPTS=e CHANTYPES=#& PREFIX=(aohv)!@%+ CHANMODES=be,k,l,cimnpqstAKMNORS STATUSMSG=!@%+ NETWORK=IRCHighWay CASEMAPPING=ascii STD=i-d :are available on this server

Implies '!', '@', '%', and '+' should be checked.

References:

http://z3.invisionfree.com/CPCN/ar/t45.htm
https://forum.rizon.net/showthread.php?1311-Channel-Management-101
http://tio.dreadworld.be/index.php?PHPSESSID=654f0jqneknr723a13g0m2lml6&topic=19.msg48#msg48