Most long-time readers of HN know where I work, and I target my comments in that direction, rather than to anyone that happens to stumble upon this page. My apologies.
(Also: never go up against the SEO blogs! They have good SEO! :)
Opinion should always be disclosed as such with disclosure and probably normally a disclaimer that it your personal view and not that of your company although if it is a statement of pure fact I think it is OK to post anonymously and/or without disclaimer.
Your comment about G+ above is very much opinion.
A factual statement correcting another post "you can now do X by going to Y" in response to a complaint that you can't do X is for me fine even if related to your employer and you don't disclose anything.
Working for myself now means I don't have to worry about contradicting my employer or embarrassing them, it is a nice freedom to have.