The parent comment seems pretty clearly an opinion as well. But this is why I often end up writing "I think" and "I believe" even though people often say to avoid doing so: I'm always afraid that if I don't someone will accuse me of stating fact without evidence when I only mean to be expressing opinion.

I believe the rule is to avoid it when you're trying to persuade because by default it makes you sound less convincing.nif you're just discussing, then to hell with the rule.