As discussed on ##crawl-dev:
Scroll of silence should create a silence effect centered on the player, but fixed in place on the map, rather than following the player around. It should start out about as big as los, and reduce in size over time (shrink the radius by 1 every turn or so?) until it disappears. This should differentiate it from the spell a bit.
This is not just differentiation but also balance. Currently, scrolls of silence can be used by melee fighters to completely level certain threats like curse skulls or liches. Yes, the scroll is rare but it's still not good. The change would hopefully make it less trivial to do that (there was also the proposal to simply remove it).
I've been meaning to suggest something like this. Seconded.
Lemuel
Whoa, I thought that was (pretty much) how it worked already. Sounds good to me.
Sounds good. This does mean that silence has to be decoupled from enchantments/durations and recoded as level effect, like the sanctuary (generalizing that might actually be worth it). We could even allow several silenced grids at the same time.
Keeping the duration variant for player and monster spells is good, too.
I'm sort of worried about this because you can stand right outside the silence and cast.
Using this implementation you'd probably only get a few casts, at best.
Anyway, will it still be as rare as the old version?
Hmm... I guess smart monsters (and all spellcasters are smart) should try to avoid the silenced area and attempt to leave it if feasible, i.e. if it only takes an extra step or two.