IRC clients interpret ^O (ASCII 15) as a trigger to clear all text formatting, including color attributes. In irssi, this control code resets the line’s formatting to plain text in the theme’s default_color, rather than restoring the predefined color and style for a specific event type (messages, notices, hilights, actions, part/quit/kick reason, etc.), virtually acting like %N instead of %n. This behavior can be reproduced even when hide_colors and hide_text_style are both enabled.