yes flushed the caches... repeatedly... still searching for the correct colorbox CSS/files...

YAY!!! Found IT: /vendor/elgg/elgg/views/default/lightbox

btw rename the /dir with graphics in it for "images" matching CSS entry...

The comment data is saved in the database always in the same manner regardless of the type of input. It's the input form where you would have to make the change, i.e. change the field from a text/plaintext input field to an longtext input field. The input form view you need to change / override depends on which field you want to change.