We should look at ISUPPORT's STATUSMSG token instead of PREFIX

modules/line_handler/core.py

@@ -53,6 +53,8 @@ def handle_005(events, event):
         event["server"].channel_types = list(isupport["CHANTYPES"])
     if "CASEMAPPING" in isupport:
         event["server"].case_mapping = isupport["CASEMAPPING"]
+    if "STATUSMSG" in isupport:
+        event["server"].statusmsg = list(isupport["STATUSMSG"])
 
     events.on("received.005").call(isupport=isupport,
         server=event["server"])

modules/line_handler/message.py

@@ -46,7 +46,7 @@ def message(events, event):
     # strip prefix_symbols from the start of target, for when people use
     # e.g. 'PRIVMSG +#channel :hi' which would send a message to only
     # voiced-or-above users
-    target = target_str.lstrip("".join(event["server"].prefix_symbols.keys()))
+    target = target_str.lstrip("".join(event["server"].statusmsg))
 
     is_channel = False
 

src/IRCServer.py

@@ -58,6 +58,7 @@ class Server(IRCObject.Object):
 
         self.channel_types = ["#"]
         self.case_mapping = "rfc1459"
+        self.statusmsg = []
 
         self.motd_lines = [] # type: typing.List[str]
         self.motd_done = False