Opinion on gentle constructive comments

Just a random question I wanted to ask AO3 writers:

What is your opinion on the occasional civil worded critic on your works? (NOTE: I do NOT condone hateful or overtly negative comments in any spaces, and I was under the opinion that anything posted public is open to civil discourse.)

My personal experience:

I used to love writing thoughtful, long comments on people's works. However, I noticed a pattern of authors being offended when they receive the slightest bit of construction criticism. I backed off from commenting since I don't want to discourage anyone from writing.

Ex: I would write a long, 90% positive comment and then post one sentence asking about something I thought was unclear and asking for clarification (a minor typo, a vague reference, a pronoun I didn't understand who it was referring to, etc.).

The most common response was, "fanfic authors do this for FREE, so don't correct my work! I'm just doing this as a hobby and your bashing kills my motivation."

A part of the older fanfic community I used to enjoy was the discourse with the author about their writing decisions. I feel like I can't really word it in a way without offending someone eventually, so I don't comment at all.

My final decision to no longer comment came from an author who used to react very positively at my past comments with the occasional gentle nudge of minor formatting errors and I got a passive aggressive response about how I can just enjoy their work without pointing these issues out since (once again) most writers do this for free.

I felt ashamed and embarrassed afterwards and promptly deleted my long time account. I genuinely never aim to intentionally hurt anyone and I still feel very bad.