Wait, can we answer the questions correctly at all? (Yes)
Prerelease is a big deal to a lot of players, so we need to be ready to answer questions about cards — and procedurally complex mechanics like double-faced cards — before prerelease.
Most of the tools for answering questions authoritatively are provided by the set FAQ that is released around the same time as the full spoiler.
Before that, I think the questions/answers get a bit more "speculative," but I've only seen a couple of questions where I felt this was a problem. So let's assume we're fine for now
"Spoilers" in titles
The name of a card is unlikely to be a spoiler in any meaningful sense, even if it's something like a planeswalker. Talking around it weirdly just makes the title uninformative. These questions will age very poorly, for no appreciable payoff in the moment.
Use specific, clear question titles regardless of whether a card is new or old.
Spoilers in questions/answers
The point of a question is to get answer. The point of answers is to answer the questions. Someone who's asking a question about "spoiler" content — leaked, official, whatever — is accepting that they'll get a response that talks about that content.
I understand that some folks like to browse questions just for fun, but I think their interests are secondary. It's on them to decide whether to look at a question or not. And if they decided wrong, it's on them to decide to stop reading.
There's only so much we can do here, especially since it's not just a "yes spoilers"/"no spoilers" thing but a complex set of preferences about leaks, rumors, translations of foreign cards, all kinds of stuff.
If something is spoiled in an SE question, it's probably... a single card? Two cards? The rules discussion of a set mechanic? Nobody's going to be posting an entire sheet of mythics here.
As long as questions are intelligibly structured, spoiler-averse users have plenty of ways to "bail out." We don't need special rules.