"He loves me."
Translation:O, beni seviyor.
direct vs indirect object
"Seni seviyorum" - I love you (direct object, verb acts on you directly)
"Sana bir kitap okurum" - I read a book to you (sana/to you is the indirect object, the verb is acting on the book directly).
This is complicated somewhat by the fact that some verbs that in English take direct object take indirect objects in Turkish and vice versa which you have to learn on a case by case basis.
In practice it is unnecessary. My guess is that course creators tried to disable a secondary meaning. Depending on context and your intonation "O beni seviyor" would mean "he likes that skin mole." :D. A comma does not entirely eliminate this meaning but somewhat reduces that chance because with the comma at least the meaning of "o" becomes clear.