"Why are people still interested in Markdown - what problem is it solving and for whom?"
I understand the question and wonder why it attracted down-votes. The executive summary of my answer: light markup is used in places other than text areas on Web sites.
Many of us use Markdown to keep formatted text in, and, ultimately, to generate valid html markup from. Markdown is not just for textareas in Web pages. Whole books have been marked up in markdown.
Markdown files are just text files with 'explicit' markup within them and so will always be accessible/editable/processable in the future. Markdown is 'flexible' in the sense that it allows alternative markup for the same output, and is 'light' in the sense that a limited range of styling and block formats are available. Compare that with LaTeX which shifts with each tex-live release, and which means that markup written some years ago may not format without hand editing on a modern LaTeX release.
There is the reference implementation available from Gruber's site, and, as others have mentioned, pandoc implements markdown in a way that can be extended. I'm dubious of the need for an 'official' specification; I rather like the scrappy streetwise nature of Markdown.
> Compare that with LaTeX which shifts with each tex-live release, and which means that markup written some years ago may not format without hand editing on a modern LaTeX release.
What? Certainly details of individual packages may change, including addition or removal of functionality, over time, but I don't even know what it means to say that "LaTeX shifts". The underlying markup language for LaTeX, which is the same as that for TeX, is very flexible, but has had the same flexibility since at least 1982, if not 1978.
I understand the idea that built-in extensibility leaves a platform, to some extent, to blame for its plug-ins; but many people in this discussion have proposed building some sort of plug-in architecture for Markdown, too.
I understand the question and wonder why it attracted down-votes. The executive summary of my answer: light markup is used in places other than text areas on Web sites.
Many of us use Markdown to keep formatted text in, and, ultimately, to generate valid html markup from. Markdown is not just for textareas in Web pages. Whole books have been marked up in markdown.
Markdown files are just text files with 'explicit' markup within them and so will always be accessible/editable/processable in the future. Markdown is 'flexible' in the sense that it allows alternative markup for the same output, and is 'light' in the sense that a limited range of styling and block formats are available. Compare that with LaTeX which shifts with each tex-live release, and which means that markup written some years ago may not format without hand editing on a modern LaTeX release.
There is the reference implementation available from Gruber's site, and, as others have mentioned, pandoc implements markdown in a way that can be extended. I'm dubious of the need for an 'official' specification; I rather like the scrappy streetwise nature of Markdown.