There were three specific points I got stuck playing Lost Pig. They were all essentially my fault, but I thought it might be instructive to mention them.
I give complete spoilers for several puzzles, so don’t read these unless you’ve finished the game.
1. Finding the coin. I visualized the fountain in a way that would have made it easy to spot an item sitting inside. Therefore I never bothered to SEARCH, since I figured EXAMINE told me everything.
2. The use of the pole. My problem here was the message the game gives upon picking the pole up. It is meant to imply that the pole is repelled from Grunk like a magnet (“feel like pole push Grunk away”), but I (admittedly not justifiably) read it more as “heavy” or “awkward” and never visualized any sort of force. This message was a one-time clue; there’s never the impression of the pole “floating” while Grunk is carrying it around. (This could at least be mentioned when examining the pole while it is in Grunk’s inventory.) Because I passed over the initial pick-up description, I focused on the EXAMINE description and the detail that the pole was taller than Grunk. I kept getting frustrated trying to set up some sort of pole vault or bridge.
3. Getting the hat. The hat is a second-order object mentioned in the description of the statue. I presumed the mark was examinable, but not anything else. Since I didn’t know I could even refer to the detail separately (most IF statues would include all details as part of the same noun) the gnome’s hint about the hat went far over my head. Because I had no hat I kept trying to get the pants wet enough that I could wring sufficient water to light the powder. (Putting wet pants in the powder gets them dry, but starts no fire.)
Renga in Blue 
FWIW, the clue that did it for me for the pole was asking the gnome about it. The other two I was also stuck on; fortunately I was playing with others who set me straight.
Yeah. I think the fountain is basically fair, although it’s unfortunate you got stuck. But I think it’s convention to have to look inside containers.
I think I also had to ask the gnome about the pole to get anywhere, but I sort of figured that was intentional — I think the effects with yourself (and with your tongue, if you LICK POLE) are more like an easter egg. Well, I guess there’s also the painting clue, but that may only work in retrospect also. The thing is that I think this is hard to clue without giving it explicitly — you can’t just have another red thing stuck to the pole because that would make it too obvious. Ideally you’d have *another* magnet which was, say, blue and picking up an orange thing, and then the player could make the leap. But that turns into kind of a mess.
The hat was a little unfortunate. I believe Jota said he’s going to be changing the interaction with the other clothes some, since right now you get a generic brush-off message for everything except the hat.
The other thing this makes me wonder about is what kind of change it would be to stick the gnome in the middle of the dungeon rather than off to one side. I wonder if the player would be (eg) more likely to ask him stuff if he was central.
I did say I considered these flubs my fault. Most of the writing I’ve seen about good puzzle design talks about getting stuck on design flaws, but I think reasons for getting stuck on fair puzzles are just as interesting.
1. Finding the coin. I visualized the fountain in a way that would have made it easy to spot an item sitting inside. Therefore I never bothered to SEARCH, since I figured EXAMINE told me everything.
That’s… not actually your fault. You simply expected EXAMINE (or X) to function as it would in any other game. Basically, this one is on Admiral Jota, not anyone confused by the irregular implementation of a common command.
It’s been a long time, but my recollection is that by default, inform treats “examine” and “search” as unrelated, and if you want to converge them, the author has to manually alter their behavior. “Search” is conceptualized by the parser as being the transitive form of “inventory” (or, perhaps, “INVENTORY” is a synonym for “SEARCH ME”)