One improvement to my life is assuming positive intent. If there is a way I can interpret someone's comment in a positive light, I do so. I'd rather occasionally seem like a fool who didn't realize he was being insulted than hurt somebody by falsely accusing them of being mean.
Okay I definitely agree with you in situations where people are being invalidating.
Tone is hard to read on the internet. Personally I read that comment as reassuring rather than invalidating. (Of course it wasn't directed at me). I get anxiety quite regularly and have battled depression since age 10 after experiencing something very traumatic. When someone manages to successfully reassure me, I'll take it. It can help break me out of my digging.