Depending upon a user's `org-agenda-prefix-format` (e.g., "%i %-10:c% t%s"), `org-agenda-highlight-todo` may erroneously pickup an icon `'display` property and then include/duplicate that icon in a new space between the todo-keyword and the priority. I chose tho fix this in my own setup with `org-plist-delete` to remove the `'display` pair of PROPERTY / VALUE from the plist of text properties that are copied to the new space " " that is concatenated between the todo-keyword and the priority.
Thanks, Keith