This is in response to the OP, not the later discussion.
Personally your comments seem a bit rude to me. I doubt I would've thought it was worth reporting but I wouldn't have wanted to play with you again after that.
Not everyone wants in other people's opinion on how they played. In fact I'd assume that probably most people don't want it. Either they already know they played poorly and don't need it rubbed in, or they don't care. Giving feedback only when it's asked for is a good general guideline to keep in mind for polite behaviour. (For boardgaming and other friend/hobby situations that is - this doesn't necessarily apply in other aspects of life such as work/employment situations, parenting kids, etc).
Also in your specific situation the other player told you that they found your words unkind (when they said you were being mean). And you ignored them saying that and doubled down on continuing to point out their mistakes - that's definitely rude in my opinion. You might have thought you were being honest rather than mean but intent isn't everything. Honesty can be kind or unkind depending on the situation. Sometimes the line between polite behaviour and rude behaviour is being able to read the room and recognize that you inadvertently said something that was a bit unkind or inconsiderate. It would have been better for you to back off at that point - perhaps saying something like "Oh sorry I didn't intend to be mean, I forgot that not everyone likes to dissect a game afterwards like I do. Thanks for the game anyway!" and then just leave it at that.
I believe that you didn't intend to be mean with your comment but not recognizing that the other person felt that it was a bit mean (and probably doesn't want to hear anymore about how they played badly) is at the very least a bit inconsiderate.
You've asked for feedback on whether being honest can be an insult by posting about this here, so hopefully my feedback will be helpful to you. This is, of course, just my opinion on the situation, but I hope it may help to explain why the other player reacted strongly to your words.
As an aside - I'm sometimes tempted to make a comment on other people's choices in games I'm playing. So you're not the only one who's ever wanted to say something like this... But I keep my mouth shut - unless they raise the topic first - because I don't want to risk being rude/thoughtless or come across as boasting, etc. Clear communication is tougher when it's text chat only, especially with people who don't know you. There's much more room for misinterpretation of a comment when you don't have tone of voice or facial expressions to go with it. When playing with a real life friend here, I don't worry about it - we know what each other is like. But with strangers, I think that being a bit more careful and taking the time to think a bit more about how my words could possibly come across is a good idea.