To filter out events like users entering and leaving channels (joins/parts/quits). Select a buffer, then right click the chat view where all the messages are. Select Hide Events > ... and click on the event you wish to filter. This filter will only apply to the current buffer. In order to apply it to all buffers, set a Default Event Filter.
Default Event Filter¶
On selecting any buffer, right click the chat view and select Hide Events > Set as Default. All other buffers should follow this filter on the current buffer unless they have their own filter set. If you have set filters in other channels and you want theme to use the default, select the target buffer and right click the chat view and select Hide Events > Use Defaults.