This is not a dupe for #49.

All I want is some markup that would allow me to comment a whole set of lines with minimal changes. Currently this can be implemented by commenting each line separately, but that means diffs and possible patches become really noisy. I find block comments very useful, specially when experimenting or deprecating config settings.

I don't think C/C++/Java/JS block comments (/* ... */) would be the right syntax (it looks alien), but maybe between #! ... #!? Example:

#! this is the beginning of a block comment.

Block comments are useful for long texts (documentation), disabling big pieces of data (useful on config files) and maybe more

#! this line marks the end of the block comment.

Now that I see it maybe that format is not such a good idea, but I think it's good not to introduce a new syntax element (as it would be the case of a symmetric marker like !#).