Make sure to first have SuperBLT installed. Click the link in the dependency list.
Optional video tutorial for installing SuperBLT, BeardLib, and mod_overrides mods: https://youtu.be/rin_sjSJIkg
mods
mods/PD2QC-master/loc
"_comment 5": "Chat Messages"
Careful not to delete or add anything outside of the quotation marks.
Adding super long messages is not only obnoxious for other players but will make the HUD huge.