Another quirk I came across was how in the Canyon View, on many emulators when you "climb down" you are greeted with "The xc ec knwall munz doesn't lead downward." It turns out the Solid Gold edition has no name for the "down" object, which probably didn't exist in earlier versions, and emulators don't tend to check the text length field for the object (0 in this case) because the string encoding uses something like null-termination. Text is encoded in 5-bit blocks, explaining how the random data stays within the alphabet. Whatever emulators do, it's still a bug in the game.
 It was an excuse to figure out how to make an Emscripten-like relooper, to figure out how to simulate blocking calls ("continuations") using exceptions, and to learn about the design of the Z-machine.
Edit: I guess I should mention for the "xc ec knwall munz" quirk that the directions are all objects, and "climb" is meant for ropes and stairs. I believe what is happening is that you can go down in the Canyon view, but "down" isn't the vehicle which will carry you there.
This, among many other bizarre bugs, is documented at: http://graeme.50webs.com/infobugs/zork1.htm
In addition to missing checks causing unexpected interactions, this approach also has the problem that the two ends can become asymmetrical, causing confusion (though this may be desired e.g. in the case of a trap-door). In the case of LambdaMOO, there's an entry northwest from the living room to the kitchen, but no corresponding entry southeast in the other direction!
When the BBC put the Hitchhiker's Guide to the Galaxy online , I loaded it up and went to work. Then I quit after about 15 minutes. I'd love to watch my 14 year old self working his way through that game. Did I have better focus? Did I have fewer things to spend my time on? Why was it so captivating then? It seems almost arduous today.
Have you played an Infocom game after a 30 year break? How did it go for you?
But Deadline is maybe a special case; it's not really a game of traditional adventure game puzzles using wacky dream logic. It's one half figuring out exactly what made each of the NPCs tick and manipulating them into doing things that advanced the plot, and one half doing mundane investigative work.
It also has one of the most brilliant uses of a text parser ever. When interacting with a certain item in the house, you're naturally going to use a specific verb. This will just give you a bland and generic result. But if the player has discovered a specific bit of evidence and realized what it implies about the crime, it's obvious that you could use another verb on that object to verify the hunch. It's also not a verb you'd ever just randomly use on an item, so even people trying to brute-force their way through the game would miss it. It ends up as a really cool way of making sure that it's the player rather than the character solving the crime, and something that would be very hard to replicate in a graphical adventure game.
Anyway, I too have a fond memory of text parsers in games, graphical or not.
Sierra's maybe weren't the best with some maddening quirks where certain word orders wouldn't work and the responses were nonsense. Sentences that had direct and indirect objects were frequently problematic: "give the mouse the cheese" would result in "you aren't carrying the mouse". I should probably blame my pre-teen english for the frustration however. Infocom games were smarter, as I recall.
KQ1's puzzle requiring writing the alphabet forwards and backwards and encoding the name "rumplestiltskin"... have to admit I never figured that out on my own. They dumbed down that in the VGA (and all later) releases accepting the name simply spelled backwards.
As for the Babel fish, while the actions required seemed nonsensical, they were each clued by the previous press of the vending machine button. It was an interactive Rube Goldberg machine. But yes, if you didn't think in exactly the same way the puzzle designer thought you would, you had to resort to combining every object in your inventory with every object in the room in order to progress.
More modern IF games are actually a lot better about not being Guide Dang It, so it's really a shame there's no market for them any more. Nelson and Plotkin are pretty good about trying to make things sensible and solvable, most of the time. For instance, there are many different ways to open the pill bottle in Curses--ways based on common sense--not just the one where you find the pill-bottle-opening-machine in the goblin lair, insert the "E" battery that you removed from a malfunctioning weather radio, and press the "open pill bottle" button, instead of one of the 999 "kill player horribly" buttons, because you read the goblin language primer at the public library that only had two books in it. (That is not in Curses, it's just an example of how Infocom might have scripted it.)
I was a bit younger than you at the time I tried the HHGTG text adventure, and only managed the Babel fish via meeting someone older who had beaten it... though my mistake was not realizing I actually needed EVERYTHING (as a kid, why grab the junk mail?), and also needed to disrobe. At least, having read the book, I knew I needed to lie down in front of the bulldozer.
"Here. I grabbed your post for you, in case you didn't have any other souvenirs. Drink up."
Modern IF games usually make it harder to get your game into an unwinnable state.
(1) As opposed to RPG-style grinding.
No way could I spend time on Daggerfall now like I used to. My life is simply too frickin' busy... I'm basically already playing real life like a RPG.
I need most things I focus on to have a legit, tangible payoff nowadays.
> With what?
> You don't have the you.
Magnetic Scrolls games came with a little bit of graphics (or, in the case of the later Wonderland game, a whole graphics environment, including a visual inventory you could drag stuff around in), and also had a more sophisticated parser. For example, if you had a green bottle and a brown bottle you could do something like:
> put water in bottle
The green bottle is now filled with water.
The internal data model was also more abstract, and therefore more flexible. For example , if you needed to cut something, you could use anything that was sharp enough, because the data model didn't require a specific object. If you had a knife, you could cut a rope, but if you also had a vase, you could break the vase, then use one of the shards to cut the rope with.
All the Magnetic Scrolls games are playable today on many platforms through Magnetic , and you can find the files online. The original Magnetic Scrolls developers were able to recover the old source code from tapes  and will be remastering the other games, and releasing the code. A remastered version  of The Pawn came out recently for multiple platforms, including mobile.