I'm too lazy to find references for all of these. I grabbed them for some.
Celestial Chameleon -- CC is a f.ds user who may very well have the highest respect-post ratio in the entire forum. This is largely due to a mind boggling puzzle he posted:
empty the supply in 4 turns. He is sometimes referred to as a god of Dominion... at least if perfect shuffle luck is available.
Edge Case -- In strategy discussion, it is often convenient to make generalizations. People say "this is true" when they actually mean "this is
usually true". In such discussions, players often pointed out specific circumstances where the rule of thumb does
not hold true. These are often interesting scenarios to discuss, and they are also a good reminder that Dominion is a game where odd and unexpected situations can arise. A specific card or action might be terrible to the point where you can't imagine a scenario where you'd want it, but you can bet that such a scenario exists. In the forum, users now take it as a challenge to find these edge cases whenever people suggest something as certain truth or take something for granted. This happens even for non-Dominion discussion.
Mine/Mint -- These two cards are only one letter off from the other. Not only that, they are both actions that interact with Treasure cards. It is easy to confuse one for the other. When isotropic was around, people often bought one thinking it was the other. People sometimes intentionally mix them up in discussions as a joke.
Scout -- This is commonly considered one of the weakest cards in the game and is thus often made fun of. Often, this is done by praising its virtues. It has a sub-reference...
Scout Combos -- Sometimes people will comment on new cards and fan cards by considering how they combo with Scout. I believe this was first done by Robz888 in one of the threads for the original
Mini Set Design Contest, but it's possible that this trend first began with previews for Dark Ages cards prior to the release of that expansion.
Is it Moat? -- For a while, "find the missing card" puzzles were very popular in the Puzzles sub forum. f.ds user Ozle would very often guess Moat.
You make your own shuffle luck -- f.ds user AdamH coined this phrase, which reminds us that we can always play better. Instead of blaming every loss on luck, we should instead consider how we could have played better.
They can't all be the best ______ ever -- This comes from a statement that was made by Donald X. People had complained about Explorer and he responded that "they can't all be the best card ever".