> What is this? It's not capitalised so it can't be an acronym or initialism.

It's a case insensitive "to be honest". Non capitalizing it wasn't intentional, but it has shown to be a prime example how case also conveys meaning.

> And your username doesn't start with a capital like a Proper Noun, so it's unreadable.

No, it's a combination of my name and surname, and a play on C/C++ header convention, more specifically "bayindir.h", which is based on a joke one of my university friends. See? Again case conveys meaning. In this case, my username is case sensitive and has a meaning when it's all lowercase. Bayindirh won't do in this case.

> it's not how humans use writing, think...

Case carries information, conveys meaning. "apple" and Apple are not the same word, doesn't point to the same "thing". Computer is the ultimate data storage and manipulation device we have, and I don't want ambiguity in any parts of it.

If humans didn't use cases, and this is not how we use writing, i can just write will all lowercase letters and make distinctions between apple the fruit and apple the company, or turkey the animal and turkey the country some other, more convoluted way. Cases matter. They carry information. Try to tell a mathematician or any scientist that their formulas are moot because X and x are the same variable.

> If the computer isn't letting me use "apple" or "Apple" interchangably as I (the user, supposed to be in control here) wish, that isn't helping me, it's nitpickingly hindering me and making me implicitly care about character encoding values I can't even see. This is dreadful UX.

I'm the opposite. I consider apple being equal to Apple "Dreadful UX", so it's subjective. IMHO, every user have preferences and a computer can adapt to that. Given the choice I'll prefer case sensitive, you'll prefer case insensitive. That's OK. What's not OK is pointing a finger to a property and calling "This is useless!"

On the technicalities side, there are some capitalization rules which make case insensitive systems shiver and break. For you probably i and I are same. For me it's not. We have i, İ, ı, I. How to make this case insensitive? A lot of programs break because of this. This is fun. This is called Turkish.

So, no. Neither a and A, nor i and I are the same letters. They don't have to sound the same either.

> Domain names aren't case sensitive, email addresses could be but generally aren't, usernames...

Case insensitive passwords and usernames are big security nightmares, including the technicalities I've described above. Names on credit cards are built upon the assumption that capitalization works the same everywhere (it isn't). Just because Google wants to match something case-insensitive doesn't make it right.

Some things are designed to be case insensitive against the norms. In normal human language case conveys meaning. Some conventions decide to ditch that meaning. Many programming languages are case sensitive. Are they wrong? No they're not. SQL statements use cases to denote keywords, even if they're case insensitive.

Case conveys meaning. Ditching is a choice.

> It's nice, convenient, helpful when identifiers aren't case sensitive.

In some cases yes, in most cases no. Try to lower() this comment, and try to read it. It may not be nice, convenient and helpful.