Subscribers and upvotes are up to you. Sometimes I do it but I'm guilty of not really thanking my subscribers or upvoters... however as for comments I'd definitely recommend responding.

It's really personal preference, but I try to

Definitely reply to all the comments. I love the interaction I am able to build with those who comments especially the ones who do so frequently. For sure you know they read your story and invested time and more to comment. I thank the subs and upvoters too just because I really appreciate them.

I like to thank every sub and upvoter cause I want them to know that I appreciate it and that they bothered to do that. I always respond to comments even if I don't know what tosay and it's just like a "^_^;;" or something... Maybe that's just my opinion, but that's what I do~ hope it helps~!

I used to thank every subs and every upvote. Now not anymore because u will get charge when leave comment on sttanger's wall. So, i dont know if it worth the effort. But it doesnt mean i dont apprraciate to all the subs and upvote given :3
But i still reply to comment (unless im just a co-author.im not sure if i should do that as co-aurhor). Just so they would know that i appreaciate their comment and feedback. After all, a comment from reader is an author's happinness. So, why not respond to it if it make u happy :) it just my opinion, btw.

Yeah you should comment back! ^^

you should deffinetly respond on the comments

it's nice doing it, but it's not always necessary. Unless the comments are some questions about the story.

It's nice to but I don't because I don't have the time to.

well if youre bored, you can

I don't mind even if the authors do not reply to my messages...as long as I feel that my comments reached the author, Its more than enough for me and also...most of the authors of AFF have been really kind to reply to my comments. You all are awesome.

It depends how many you get, I reply to every comment unless I don't have anything actually important to say. So if you're just going to say thanks for commenting then don't thank individually, thank in the authors note, just like subscribers. I mention everybody who upvotes by name cause it's something that's really important. I love comments but since upvotes means that my story gets out to more people I like to give shoutouts to encourage them.

Tbh it's really up to you, cos it's a personal preference. To me, I thank all my susbcribers, up voters and I reply to all comments on all my stories because I think that by doing this, you are showing your appreciation and gratefulness to your readers.