There are absolutely ways to ignore casing here. Unfortunately, one of the tests written requires case sensitivity, so your function might be perfectly correct and still fail to clear this kata.

Explicit is better than implicit.

And you earned one point.

Sounds fair. :]

OP solved it, closing

No. Actually by using toLowerCase(), you are doing alright.
You might as well use toUpperCase.

"ignore letter case" means that when you compare two letters for equality, it does not matter what case they are. For example, S and s should be treated as the same.

Because this is the specification. In this problem, words like "Anita" or "Shrimps" are not isograms.
The same or different "unicode characters" is not really relevant. "unicode characters" is a technical thing, while "letter" is more of a language concept. Bringing technical concepts into the domain of the problem is a mistake.

When writing real code, clarity is the most important rule in practice, beyond doing smart tricks. You do NOT need to use bitwise operations in non-bitwise-based logic. We only did it because we're used to code golfing.

You declared the 'sum' identifier, but never used it.

Unfortunately, your solution is not right yet. The expected funciton name is howManyDalmatians. But even when you fix this problem, you still have more than one bug to squash.

Not a kata issue you need to keep squashing.

Okay, but what's the suggestion? "Suggestion" label is for suggesting changes to a kata. 8 kyu katas aren't supposed to be challenging.

You're not doubling it, you're squaring it instead. Not a kata issue.

define "wrong"

maybe what you're testing locally isn't what you're failing. passing one test isn't a very strong promise of that it's going to pass all the rest.

if you describe the problem as only "wrong" then the problem may be that you're not looking at what is happening! you've got console.log for that.

if you must post code, use the spoiler tag. ideally avoid it completely.

running your code in the kata produces error messages saying that you return "undefined". what does return mean?

Your code only replaces the first occurence of each number.