I recently realized a colleague posts several times a day to the website Reddit. If the opinions he shares on this site are about his boss or his work environment (or even reveal his political leanings), he could potentially lose his current contract and have a hard time getting a new position in our insular field. I find this colleague to be immature and ill suited for our profession — he seems to spend most of the day posting on Reddit — and some of his posts have made his identity obvious to me. Do I have an ethical obligation to tell him that this behavior could hurt his career? NAME WITHHELD, PENNSYLVANIA

You’re making a lot of assumptions here. For one, you note that this colleague could lose his job “if” his opinions relate to his employment or his politics, which suggests you haven’t actually read anything that fits that description. Also, you seem to suspect this colleague has absolutely no idea that such behavior could result in dire career implications. Now if that’s true, you should tell him otherwise (out of professional and human courtesy, just as you would with any young colleague confused about his livelihood). But I would not presume he does not realize this. At this point in human history, it’s unlikely that any adult heavily engaged with the Internet is clueless about its potential downside.

Here is what I would do: Casually tell the guy, “You probably shouldn’t be posting on Reddit during work.” In all likelihood, he will ask how you knew he was doing this. Proceed to tell him that you simply deduced it from contextual clues, and that if you could figure it out, other people in the office almost certainly can, too. That should tell him everything he needs to know. If he totally disregards your input, he’s as immature as you insist. He’ll either learn his lesson the hard way (by eventually losing his job), avoid detection forever (because maybe no one else is looking) or simply exist as the kind of person who has an online life that’s totally unconnected to his work life (because I feel as if the culture around that dichotomy is migrating toward acceptance and disinterest).

Also: You should probably assume this letter will now be posted on Reddit. Although that probably won’t surprise you, as it appears you already invest a fair amount of time reading and analyzing its content.