It is now possible to merge buffers with command /buffer merge (or unmerge). IRC plugin uses that feature to merge server buffers, with the new option irc.look.server_buffer (merge_with_core, merge_without_core, independent).

When a buffer is merged to one or more other buffers, they will have same number, and chat area will display mixed lines (short name of buffer is displayed on each line, to know to which buffer line belongs). Bars still display content for current selected buffer.

New key Ctrl+x has been added to swtich current active buffer when many buffers are merged (old key Alt+s has been removed).

For devel users: it's not possible to upgrade from previous versions to this one, and you should do /key missing to add missing key.