The closing tags of HTML and XML are a nuisance. In SGML (their common predecessor), named closing tags were optional (you used </>), but were deliberately made mandatory in HTML and XML, to improve readability of long documents. It was contentious at the time, and it still is. But we must at least accept the data points that both HTML and XML have been
phenomenally successful, without knowing for sure whether this particular feature was for or against.
One thing about dumb, regular, symmetrical formats is that their redundancy makes them less scary and easier to understand. Perhaps, this is accessibility is crucial for adoption.
EDIT I guess indentation enables you to match up start/end tags even better than named close tags... and it's certainly become more familiar to developers since Python's success. But maybe not so good when you have many levels of indentation, and terrible if you want to insert/delete a nested element, because the indentation of the elements within it must also be changed.
One thing about dumb, regular, symmetrical formats is that their redundancy makes them less scary and easier to understand. Perhaps, this is accessibility is crucial for adoption.
EDIT I guess indentation enables you to match up start/end tags even better than named close tags... and it's certainly become more familiar to developers since Python's success. But maybe not so good when you have many levels of indentation, and terrible if you want to insert/delete a nested element, because the indentation of the elements within it must also be changed.