In the DS mudlib (LPMUD), there are also SetSmell() and SetSound() functions which provide seperate audio and scent information. Been that was since 1995, so it's nothing new. It falls to the builders to make use of such things, and they rarely do since players are accustomed to visual descriptions.

If you want a thought experiment though… imagine you have a race of creatures like ferrets, where scent is their PRIMARY navigation sense. To them, the world is made up of thousands of scents that uniquely identify everything near them. To a human, 99% of those scents are undetectable, unless the object is literally right under their nose.

Now, you're building for a MUD. Do you expect your builders to actually add scent data to EVERY room, EVERY object, and EVERY NPC, so that players who choose the CthulhuFerret race can see "realistically"? Because you'd actually need to do that. You'd give each race a smell threshold range, just like I described with light. Humans can smell scents in the range of 120 to 180, only overpowered by 180+. These ferret-like creatures would smell scents in the range of 10-150, "blinded" more easily by stuff that's just a semi-strong smell to humans.

How many players are going to think that's such a cool thing that they'll play because of it? How many will notice? How many would just turn brief on for all their senses and continue typing n;n;n;e;e;e;e;e;e;n;kill smurf?

The best way I've thought to modify room descriptions in "adverse light" is sector type. So instead of the description, it'd show:
Mountain
A mountainside stretches upward…etc.

Beings could be race and age:
An elf of some years is here.

Also meeting that exact elf before could allow the name to be known because people recognize shapes quite easily.

Things maybe by size and type:
A small weapon is here.
A large container is here.

…and "is here" could be randomized with "is sitting here" or something equivalent. It might be really cool as long as it isn't completely baffling.

A friend of mine Erik Grow (Zaunstar) recommended leaving out words to achieve vagueness, though he said that would drive people crazy. Randomly leaving out characters looks like this:

Th Temp Of Mid aard
o are in the o th rn end o t te ple all i e mple f M g ard.
The tem le as been co s u d from gi n arb e blocks, eternal in
L rge st ps a own thr ugh the rand tem le gate, desc ding th uge
nd upo wh t e t e s built nd ends on th t mp e s uar el w.
(W i e Aura) Th x cu on r i her p lishing s blade. is n this all.
T exec tione l oks t
<2 p 00m 4 v
The drunk ll 'Mo ster I fou a mon ter! Kill a a !'.

h 10 m 100mv>
You disa pear into the id.

The Murk++ test code for this is:
std::string dim_txt = txt;
for (unsigned i = 0; i < dim_txt.length(); i++)
if (number_range(1,4) == 4)
dim_txt= ' ';
outbuf.append(dim_txt);

The number range could vary depending on the player character's visual acuity, allowing some percent of a description to be seen.

I can't believe you actually coded this :)

This reminds me of the fact that we can all benefit from implementing fewer things that drive players crazy and drive players off. It's not like we can afford it.

It's one of those issues of scope. Obviously it's an awesome spell to cast on someone. Is it something awesome MUDwide? Maybe enough players think so.

Heh, I would probably have ensured the first and last letter of each word was intact, and scrambled the rest. Somebody did a study a while back, sohwnig taht msot popele culod slitl raed txet as lnog as teh bunordeis rmenied itncat.

Of course, the closer to "correct" it is, the easier it is to scan.

Hehe, really? Then how about a spell that temporarily disconnects someone to imitate a fugue state? Should be pretty great for PvP, and very easy to implement…

What's obvious to me is this approach is a bad punt on a limited visibility implementation. If you want to have the quantity of light affect room descriptions, the right way to do it is to have different descriptions for limited-light conditions, as KaVir outlined. Less light in your virtual world doesn't/shouldn't mean that your server output is partially chewed up. It should mean that the descriptions of the surroundings lose definition, not random letters. Unless you're running a kind of meta-fictional game that is aware of and plays upon its own medium, in which case feel free to steal the fugue state spell idea :)

Most interesting would be to degrade visual feedback during the night, smaller line of sight, less details. Could be more difficult to tell races and genders apart, or whether you know someone. Smells could be handled depending on the wind direction. Might be able to smell a group of orcs before you see them.

A blue dragon might be difficult to tell apart from a green dragon in a dark cave full of smoke. Most (if not all) MUDs are horribly binary in this regard. The implications for game play could be fascinating.