Is it just impolite not to use brackets like PHP or are there other reasons not to?
With some sort of brackets (or block delimiters), it's easier to specify the syntax of how the various languages on the page are intertwined. You need to specify the syntax of the page in order to build a parser for it. Without brackets it might be impossible to specify a syntax, or the syntax (and the parser/preprocessor) might be horrendously complex.
I can't imagine that will be easier to type than a single block opening and closing as in other languages (such as PHP, JSP, ASP, etc). There are very good reasons all of those very popular languages use almost identical block identifiers, maybe take a few moments to read the html spec sheet so you can fully grasp what impact your "adjustments" might make to parsers.
I'm thinking of including these text nodes within a master <div>.
That way, they would validate and be loose text nodes...
Handcraftedweb - what do you think?
I'm assuming you're preprocessing this on the server side, in which case the input doesn't need to be valid HTML, the output does. The input does need to have well specified language/syntax and the preprocessor will act as validator for the new language.
So you don't need the enclosing div but I guess it wouldn't hurt.