In your last encounter with Naryu Virian in the base game, you can imply to her that you'll be there for her if she ever needs it. Her response is to tease you about always being the hero, blow you a kiss, then say that she would like that and will find you if she needs your help.
At the end of the Orsinium DLC, Eveli Sharp-Arrow has nothing but words of praise for you, thanking you for everything and for being the one person she never lost faith in.
A quest in the Dark Brotherhood DLC has you reunite with Mel Adrys, a Dunmer vampire hunter who you assisted in Greenshade. The two of you hunt down more vampires together and if you are a vampire yourself, he comments on it. According to him, he considered killing you as well, but having heard tales of your exploits, he believes that you will do more good than ill and allows you to depart in peace.
He was also nearly killed in the time between his quest in Greenshade and up until you meet him again, but was saved by Aranias, now the Wilderqueen. When he asked why she saved him, her response was, "Thank the Vestige." Even now, it seems she considers the Vestige a friend and a profound influence.
In one of the Thieves' Guild DLC quests the bitter and abrasive Dark Elf Velsa tells you to investigate an anonymous letter she was sent that was somehow connected to her past. She suspects it's a trap by her slave-trading family that she fled from long ago. Instead it turns out to be from one of the Khajit slaves she freed...her former lover Nahrani, now an old woman. Their reunion in Velsa's hidden villa is both heartwarming and the good kind of Tearjerker.