Pidgin is a tool for using lots of different communication protocols, like XMPP, irc, icq, and even lots of closed ones via plug-ins (Steam, discord, facebook, mattermost…)

To add more dictionaries to the spellchecker (gtkspell) you gotta search for hunspell packages.

In Arch these look like hunspell-en_AU. They are spread throughout extra, community, and the Arch User Repository.