I saw a post a long time ago saying it was vanishing due to rise of smartphones but now it has VANISHED. Authors of both art/fanfiction,books,etc generally can't handle beyond 'Cool' or 'Thanks' this has caused realistic authors to sometimes ask why they CAN'T get any lengthly reviews and I can tell you why if your one who seeks feedback:

THEY DON'T WANT TO GET THEIR HEADS BIT OFF!!! Simple as that. A02 is worse at this as it's all designed for authors to have full control so people are NOT going to give a detailed review knowing their comments can be deleted at a whim over something minor.

Hell I deleted my account as I wanted to do a short story but since it's mostly women and when they reveal where they are from the majority are Canadian and don't give a crap about how you feel if their character is a total dick. The character 'clashes' often seem forced to promote dividing like the author is trying super hard to force a debate instead of letting events play out naturally.