Loving tendonna feels like:
Picture of Ten and Donna has been cropped out of the picture
Picture of Ten and Donna being cute and the caption/comments are flooded with "omg the besties ever!!!! Sibling coded, my comfort friendship!!!nHow could anyone ever ship them????? How disgusting and stupid and wrong would that be????"
Random person writing a single fic with them in a pairing as a joke, it must be implied that the only reason Ten would be interested in her is if he's a raging sex fiend for any woman. Donna is #socoolandunbothered and super sexually available.
If not the above scenario, it's somebody writing untagged noncon where they're forced together, or they must throw in a line about how he would far prefer R*se but his silly old hag of a friend would never expect more out of him!!! Not like Donna canonically demands his respect or anything!!!