Online users appear offline on irc.mozilla.org
On irc.mozilla.org, often users appear offline (i.e. their nicks are grey and they don't appear in the user list in the header bar) when they are online. It's usually most noticeable when it's the currently-speaking user or an always-online bot, but to check I've also compared the list of online users with what HexChat shows. For example, HexChat reports 163 users in #nightly right now but Polari reports 115.
This doesn't seem to be a problem on chat.freenode.net.
Edited by Peter Simonyi