Hiding Portaits in Chat

I've done some pretty minor extension creating/editing in the past (making a MoreCore skin for an Infinity game, setting up character templates for importing, changing some labels of various areas on the character sheet, changing some graphics, resizing some elements, adding a custom dice string, that sort of small tweaks), but I've never had to mess with stuff inside of the chat window before.

Until now!

There used to be a setting in the option list "Chat: Show Portraits". It defaulted to on, but I greatly preferred to toggle it off. It appears that option has been deprecated however, so I'm looking at adding it back through an extension of some sort. Thing is, I'm not quite sure what files are involved with messages getting posted and displayed in chat to begin with. I'd appreciate any pointers to help me on my way!