524 is already used to notify about Quarantined channels, it would not be good to bind it as "help not found"

Yes, but ERR_HELPNOTFOUND is more widespread:

• 524 is ERR_HELPNOTFOUND on irc-ratbox and derivatives (Hybrid, Solanum, Plexus, ...), InspIRCd, and Ergo. This covers 6 of the top 10 networks (according to netsplit.de).
• UnrealIRCd may also start using it as ERR_HELPNOTFOUND in a few years depending on client support.
• 524 is ERR_QUARANTINED on ircu2 derivatives (Nefarious, snircd, ...) except UnrealIRCd. This covers 2 of the top 10.

What do you usually do when numerics clash between servers?

we would need to detect which one it is, probably by using a strcmp and see if the response contains :Help, so that we can display the right one. quarantined channels also contain the quarantine reason, wouldn't want to hide that for sure

Hmm that might fail because :Help is not guaranteed to be a substring of the ERR_HELPNOTFOUND message.

However, we could check if the second parameter starts with one of the ISUPPORT PREFIX character; it's unlikely to be a valid topic name. Agreed?

sadly that's not so cool either, if we do /shelp #xxx then it would trigger the quarantine code path??

maybe just leave the 524 unhandled (sad but less work)?

Edit: according to https://www.alien.net.au/irc/irc2numerics.html, 524 could also be in use for ERR_OPERSPVERIFY

Ah, sad. I'll remove it, then.

thanks for the improvement, merged into ailin-nemui#82