As mentioned in the related answer, the red dot in the fringe signifies a bookmark. The OP tried to suppress it by setting
org-capture-bookmark to nil, but that does not work:
org-refile uses a bookmark, but it is a different bookmark.
By extension, one could imagine that there should be a variable
org-refile-bookmark that could be set to nil to suppress the
org-refile bookmark, but there isn't one: probably an error of omission.
However, the bookmarks that Org mode uses are stored in a different variable
org-bookmark-names-plist. This is a plist as its name implies with the default value
(:last-capture "org-capture-last-stored" :last-refile "org-refile-last-stored" :last-capture-marker "org-capture-last-stored-marker").
This variable can be customized (do
C-h v org-bookmark-names-plist and click on the
Customize link) to eliminate whichever bookmark(s) one does not care about by clicking on the
DEL button(s). If I delete the
:last-refile entry (and restart emacs), then the
org-refile bookmark is not set for me. Restarting seems necessary only in the sense that the red dot in the fringe does not seem to go away otherwise, even though the bookmark is not set (although there might be a simpler way to reset the fringe).
If you don't want any bookmarks, you can delete the other entries in the customization buffer as well, then hit
Apply and Save and restart Emacs. You will never see these bookmarks again.