Honestly, I used to just let threads drift until they became unreadable, so I get why this feels awkward. The trick that works for me is to acknowledge what they said first, then gently steer back. Something like, "That's a fair point about XL live arcade games, but I don't want us to lose the original question about forum etiquette." It validates them without calling them out.
A private message often works better than a public reply. Public corrections can feel like shaming, even when you use soft words. I once watched a mod handle this beautifully by saying, "Quick reminder that this thread is for digital wellbeing tips — feel free to start a new one if you want to discuss play Pragmatic Play slots online." Nobody got defensive, and the thread recovered.
One thing I avoid is using "but" right after a compliment. "Great insight, but..." reads as fake. Instead, I separate the two thoughts: "Thanks for sharing that. To keep this thread useful for people searching, let's circle back to the main question." The word "useful" frames it as a shared goal, not a personal complaint.
If the off-topic posts keep coming, a short note like "This is drifting toward online casino with crypto deposit territory — maybe we can split that off?" gives them an easy exit. And if you're a regular, leading by example matters more than any phrasing trick. People mirror the tone you set, especially in smaller communities where a few active voices shape the whole culture.