When I began switching over to Pandoc a couple of months ago, I searched extensively for some way to specify centred text in Markdown, and found a syntax extension that numerous end-users advocate, but no tool I know of supports:
>
> Basically, the Markdown text (potentially contained
> within some larger construct) is bracketed with little
> ASCII-art arrows, like so:
>
> -> This paragraph
> is centred. <-
>
> ### -> This level-3 heading is centred. <- ###
>
> -> This level-1 heading is centred. <-
> ======================================
>
As I said, numerous people online claim this works, but I have yet to encounter any software that actually supports it.
It seems simple enough in principle for us end-using peons to support, at least when using a custom writer. It appears that any kind of text that might qualify for this treatment will be passed to one of Para() or Header(), which can then special-case based on finding or not finding literal ASCII-art arrows at the beginning and end of the given string argument. I conjecture that it might also turn up in Plain(), but I haven’t yet figured out just what circumstance causes that function to get called.
There are two obvious questions here that Mr. MacFarlane or someone equally “dialled in” to the Pandoc project can save a lot of trial and error by answering:
1) If someone, just to be difficult, needs to have literal ASCII arrows at the start and/or end of their actual output text block, can it be accommodated in a simple way by backslash-escaping? At what stage does that get stripped out — before the custom writer functions get called or after?
2) What would be involved in modifying the Pandoc markdown parser to recognize the obvious extension to this syntax, demonstrated below?
-> This text should
-> be right-aligned
-> in output formats
-> that support that,
-> without being
-> mistaken for a
-> block quote.
While I’m on the subject…
-> Right-alignment
-> and centering
-> should also…
-> …work with
irregular
margins, for
obvious reasons. <-
If it simplifies anything, I find it difficult to envision a circumstance where someone might need a centred or right-aligned block quotation (the closest I can come is where someone’s abusing HTML blockquotes to get a narrower canvas for part of the document), so the two notations can easily be defined as mutually exclusive — a good thing, as it would likely look terrible in the original formatting, thus violating a key design goal of Markdown.