regarding the correct/incorrect use of the comma [duplicate]

Let's be a bit more descriptive than prescriptive about our grammar rules...

If you're writing the sentence, you get to decide how you're saying it. As long as what you're writing matches what you're trying to say, you're good.

Commas represent pauses in speech. In comparison to a period, they're shorter, and imply the two statements aren't really complete and independent without each other. One great rule I heard in college described the four pausing punctuation marks this way:

, < ; < : < .

So commas are short pauses, semicolons are kind of a strong comma, often used to separate lists of statements/ideas (usually with a colon). Colons have a little more wrapped up in them than the length of the pause, if actually implies a connection between two ideas that probably could stand on their own as separate sentences, but the first is implying or so significantly modified by the following one that you almost want to put an arrow between them. The colon acts as that arrow. The period flat out says this idea is complete, moving on to the next one.

So when you're punctuating, just think like a director instructing the reader how to say it in their minds. How long is that pause supposed to be?

With that said, the second one stands out as how I'd say it.

There is a building which is taller than all others, known as the Burj Khalifa.

The first could leave some ambiguity. Is this building taller than ALL others? Or is it just taller than all others which also happen to be known as the Burj Khalifa. In this case that would be silly, but say thirty years ago you were making the statement about the World Trade Center. There are a lot of World Trade Centers, so that could be the case. I mean, if someone took it that way they're a doofus, but you could make the argument.