When typing a comment on most objects, user gets to see a preview of the entry under the text field. The preview usually contains the author's profile image, and the image is large enough to display badges under it, like other major events in the object's timeline. So far, it's been tricky to narrow down where the preview is building the profile image html. PHUITimelineEventView.php seems to have part of the preview in a method called renderExtra(). To figure out if this task is trivial or not, it would be helpful to locate the correct code where the comment preview is built, so it's assigned to @epriestley for now, in the hopes that I can be pointed in the right direction.
See also T8941: Badges don't show in certain Timeline conditions and D15543: Changing criteria for showing badges in object timeline view for context.