It is weird seeing how all other words have only one meaning.
This is my recollection from years ago, so the wiki has likely been changed since then. Possibly even by me.
Well, for most of the history of the word, ‘fish’ and its predessors referred generically to ‘sea critters.’ And some of the ancient words for whale were (in translation) ‘whale fish.’ Not sure when it was decided we shouldn’t we should separate out mammals.
BTW, ‘Sea Critters’ was my favorite restaurant in St. Pete Beach. So sad when it closed.
Not surprising that it took less than 20 posts for this joint to shift from “Examples of nit-picking” to “Defending nit-picking” 
On a different forum, I was once engaged in a thread about a politician busted for molesting kids and one poster repeatedly wanted everyone to know that, once the child was 11, it was hebephilia and not pedophilia so no one should call this politician a pedophile for his crimes. He went on to justify this by saying that it was only because he hated pedophiles so much that he couldn’t stand to see the term misapplied and anyone calling this guy a pedophile obviously just didn’t care as much about “real” pedophilia as he did. Had nothing to do with his outspoken politician alignment matching the party of the busted predator.
I don’t know how he expected that to play out in his head but, naturally, everyone responded to this in the obvious way.
Further on the whale thing, a whale is more closely related to a trout than either one is to a shark. So if it makes sense to make a category that includes both trout and sharks, one can certainly argue that whales belong in that category, too.
You’ll often hear “well actually, X is an ape, not a monkey”, but it’s rather more nuanced than that. Cladistically, apes are a subgroup of monkeys. Common usage tends to use “monkey” to refer to all simians except apes, but excluding apes from other simians doesn’t have a reasonable biological basis.
A nit to one is pretty lousy to another. 
FWIW I draw a big distinction between the people whose corrections are at least correct, just not of any matter in the conversation, and both distracting from the meaning of the conversation and uninteresting as an independent factoid, and those that are both not worth raising and wrong.
How many states are there? 50, of course. No, there are only 46 states, and then there are 4 commonwealths: Kentucky, Massachusetts, Pennsylvania, and Virginia. That’s a distinction without a difference. They can call themselves commonwealths but they’re still states regardless.
After a bad pun like that, you’re supposed to flea.
Dad got his PhD in Herpetology and uses poisonous and venomous for snakes pretty much interchangeably. However, he is almost 96 and I have wondered if this is a generational thing.
Basil Fawlty: It’s always a pleasure to find someone who appreciates the boudoir of the grape. I’m afraid most of the people we get in here don’t know a Bordeaux from a claret.
Mr. Walt: A bordeaux is a claret.
Basil Fawlty: What? Oh, Bordeaux is a claret, yes, but they wouldn’t know that.
“That’s not a Motorcycle! That’s a Scooter!”
These days, pretty hard to draw a distinction of some stuff.
If the person happens to know a bit about brewing, the bitterness of beer is a great example: it comes from the alpha acids in hops. They’re already somewhat bitter in their natural form, but after isomerization during the boil, they convert into iso-alpha acids, which are significantly more bitter.
And then there’s astringency, which isn’t a taste per se but more of a tactile sensation — that drying, puckering feeling you get from tannins in red wine or strong tea. It’s often confused with bitterness, but it’s a different kind of, well, I don’t want to say “unpleasant” as it can be pleasant, but you get what I’m talking about.
I do find that either a lot of people confuse what bitter and sour are, or I simply have a different experience of bitter and sour. I swear it feels to me like a lot of people use “bitter” as a synonym for “sour.”
I’ve definitely seen people use “bitter” for the flavor of lemons.
Lemons do have an aspect of bitter, but the overwhelming flavor to me, at least, is the sour. Though I suppose some people are more sensitive to bitter than others. (I am probably less sensitive as I love bitter flavors of all kinds.)
There is also bitter lemon flavoring which combines bitterness and sourness. I don’t expect the average person to be all that good at identifying flavor quality.
Completely unrelated, but scooter reminded me of schooner
I think of lemon peel as bitter. Lemon juice as sour.
I concur. And reminds me of all those recipes who state that you should add a spoon of sugar to your tomato sauce, because otherwise it will be sour.
So first: I never add sugar to my tomato sauce, and it is never sour.
And second: the chemical opposite of sour is not sweet, it is alkaline. To counteract sour in your sauce, assuming you need that at all, which I dispute, you should use something alkaline, like sodium hydroxide.
Lemon peel definitely has bitter, with the pith being both bitter and astringent.