What you wrote was cleanly executed sarcasm on its own. The /s is only for people who don’t know what they’re doing, you can remove it.
Pure sarcasm has no such prerequisite, which means that delivery alone (tone, cadence, and smirk) is almost always sufficient. These give away the fact that sarcasm is happening to roughly the same extent that "/s" does, just that we have more experience with the former so the latter tends to feel too spoon-fed.
And even if someone wanted to challenge me on that, I’d argue that the tiny number of people who would think “HN is a tech support site” is being said seriously aren’t worth the two seconds it takes to type “/s”.
That amount is larger than is available in most (probably all) HN comment sections.
Not clear sarcasm.