Is it rude? Yes. *Mostly* because that brace style is *ugly as sin*, but also because you're imposing your personal preferences on someone else's writing without good cause. 

But yeah, mostly because that brace positioning style sucks. 

That said, if doing so helps you trim down a code block so that it can be read without scrolling... *AND* you're making [other substantial improvements][1] at the same time (indentation, formatting, grammar, tags, etc.)... Then go ahead.

###Related: http://meta.stackexchange.com/questions/131104/etiquette-on-editing-source-code-formatting-for-style-preferences


  [1]: http://blog.stackoverflow.com/2009/04/in-defense-of-editing/