The phrase “I’m sorry” has two core meanings. One is expression of regret or remorse for an action on the speaker’s part, and the other is an expression of condolences and sympathy.
I’ve noticed an interesting tendency for people to say things like “It’s not your fault” or “No need to apologize” when they hear this phrase after sharing upsetting news. The person who said it knows it isn’t their fault, so why do we feel compelled to tell them this?
My theory is that it centers around the fact that there is a social standard for how to respond when someone expresses regret, but there is no such standard for when someone expresses condolences. It feels awkward to say “Thank you” or other words of appreciation, so we’re left with responding to it with our defaults for if someone is apologizing.
I propose that the new social convention be silence and a nod. This expresses acceptance of the condolences without the discomfort that comes from expressing gratitude when experiencing distress. It also alleviates the awkwardness that comes from telling someone it’s not their fault that the upsetting thing happened.