Since you didn't have the opportunity to flag the comment (which is the preferred course of action), raising the matter on Meta is an option. However, it's not usually The Best Idea™ to raise this sort of thing in public: the general advice is (a) flag; (b) flag something else of the user's; (c) contact moderators in chat — we can open a private chatroom; (d) use the Contact link at the bottom of every page to contact SE staff.
The comment is, on its own, rather cryptic. However, it is (I judge) a violation of the "Be nice" policy.
- Rudeness and belittling language are not okay. Your tone should match the way you'd talk in person with someone you respect and whom you want to respect you. If you don't have time to say something politely, just leave it for someone who does.
- Don't be a jerk. These are just a few examples. If you see them, flag them:
- Harassment and bullying. If you see a hostile interaction, flag it. If it keeps up, disengage — we'll handle it. If something needs staff attention, you can use the contact us link at the bottom of every page.
Also, using the comment system as a private messaging channel — waiting for the notice to appear in the recipient's inbox and then deleting the comment — is an abuse. Comments are provided in order to allow asking for clarification or pointing out an egregious error in a post. Occasionally, a witty remark might be made in a comment and might resist deletion. However, excessive commenting is a template we have at our disposal in moderator messages, and abuse of the system — especially in what may be considered an underhand way — is unlikely to end well.
Note that we are not really at liberty to discuss individual users, their age or other personal circumstances or their past history, so I won't. Nor will we comment on this individual case other than the general statements in this answer. There is probably enough here to read between the lines.