Runes are not useful for plenty of reasons, but I think all they really need is to stop making a huge noise and instead be silent.

The problem is, this appears to be impossible. I have tried everything I could think of. In my test file, every single thing that has any connection in any way has been silenced, and yet they still alert enemies. I've ripped the thing apart and put things back in piece by piece, and no matter what, if the spell has a projectile at all, it will cause noise and alert enemies as soon as it impacts the ground.

I'm posting this in the hope that someone has an idea of how I could make runes silent.

You know, there is a perk for that. Silent Caster makes spells silent for those sneaking, quiet mages.
Alternatively, you can open up editing box for the spell you want quiet and set casting volume to silent. Not sure if that works, but there is an option to make them silent.

Edit: Didn't see that you had already tried. Sorry.
I guess Silent Caster is your call.

Quiet Casting eliminates casting noise. Taking it means your casting of spells won't generate noise at your location. It has no effect on impact noise, which is the problem here. Runes make an incredibly loud impact noise that enemies can detect for a very long range. This loud noise makes them worthless to sneak characters. It ruins sneak attacks, plus it immediately throws you into combat, so the high cost of a rune isn't worth using for its low damage. Runes would only be useful if you could stealthily place them before combat without getting into combat because of them.

Nothing I've tried has ever been capable of stopping this noise, at least while still maintaining function. I can of course remove any projectile from the spell, causing it to never impact at all, but that obviously breaks the entire function. No matter what I do with anything connected to the magic effect, no matter how I set them all to silent or even remove their actual sounds, it all is still getting detected.

Then, I do not know.

It looks like Lightning Rune uses effect RuneShockFFLocation which in turn uses ShockFXShader for Hit Shader. ShockFXShader has an ambient sound of MAGCloakShockLPSD. which seems like it might be the culprit. Just a guess.

Tried it. As I said, every effect connected to the runes has been made silent, and I even tried removing the actual sounds. It's maddening, but I simply cannot figure out how to make a rune truly silent.

Might as well give this a bump.