That's debatable to some point. What could be common knowledge to you, could be brand-new information to someone else.

Imagine this scenario:
A newbie registers a new account on Bitcointalk and starts a thread asking what bitcoin is and what it is good for? That's his first post. In his second post, he writes that same statement you did. The chances of him knowing about hardware wallets and best methods for long-term storage don't look so good if he is struggling with understanding what bitcoin is. It's not impossible that he heard about hardware wallets from some article or a video he saw and he remembers someone say something like that.

If that is the case, did he try to plagiarize and get away with it? Was it maybe unintentional? Is he trying to make it seem like the statement is originally his or does he just have a good memory and remembered the words with no intention to plagiarize? I wouldn't want to be the one making the final decision.