Block quote marker revision

[notriddle]

This is the simplest fix #460 that I can think of that matches the behavior of the reference implementation. It's not simple, because the behavior being described is complex, but it needs to be spelled out.

[wooorm]

First, there should probably (at the top?) be something about → representing a tab in this document.
I would personally recommend a control picture instead: https://en.wikipedia.org/wiki/Control_Pictures.
The character ␉ could be used to represent a (horizontal) tab.

Second, the term “marker” to me sounds like it would only be the >. With spaces/tabs after it, a term like “block quote prefix” seems clearer for me?

Q: Is it intentional that you use “list marker” on L3731? Should that not be about block quotes?

Last, as we are discussing changes to block quotes, I wonder: could we “eat” the entire > + ␉, if a tab was used?
I am assuming that a user who indents with tabs means the ␉ as an entire indent, not mean one space “of” that tab, and the rest will go to the indented code / list?

[notriddle]

First, there should probably (at the top?) be something about → representing a tab in this document.

Already exists.

commonmark-spec/spec.txt

Line 288 in 260b808

In the examples, the `→` character is used to represent tabs.

Q: Is it intentional that you use “list marker” on L3731? Should that not be about block quotes?

No it's not. Thanks! That was a good catch.

Last, as we are discussing changes to block quotes, I wonder

No, I'm not discussing changes to block quotes. I'm discussing changes to the specification language to match what the reference implementation, and any other implementation that forked or imitated it, already does.