I too am perplexed by the negative reactions you've received.
I've often been known to comment on legal matters on HN, but I always steer clear of giving legal advice. (At least I hope I've never slipped up and done so.) And, as you well know, that's the proper course for anyone, regardless of whether they're a lawyer or not.
So just to echo and build on jsprinkles' various comments: It's OK to discuss the law in a general sense. I.e. you can talk about how things work, without giving an opinion as to the case at hand. But it's irresponsible and generally illegal to advise an individual on how s/he should proceed.
Example of a comment that's OK: "Trademark disputes often depend in part on the likelihood of consumers being confused by the respective marks."
Example of a comment that's not OK: "Trademark disputes often depend in part on the likelihood of consumers being confused by the respective marks. Since the OP's mark isn't going to confuse anyone, the plaintiff will probably lose."