Not burned in the sense that I executed some hidden commands in the terminal, but I've tried pasting snippets of text in IRC and ended up pasting several lines of text that absolutely did not select.
While this may not be a huge issue in practice, I have no idea what motivates the inclusion of functionality that manipulates the clipboard in the browser. I don't really think that the analogies of anyone swerving on the highway or someone poisoning your pizza apply. It's more like your seat belts were deliberately removed, or someone put arsenic right next to the pizza box just in case anyone would want to poison you.
Technically, they're not manipulating the clipboard at all. That is definitely disallowed by browsers. What they are doing is extending the selection to an invisible part of the page, so you're copying more than you bargained for.
But without being able to manipulate selections, some nice features of certain sites would be lost. (e.g. the "share" link in StackOverflow automatically selects the URL for you so you only need to press Ctrl-C, instead of having to select it manually.)
> I have no idea what motivates the inclusion of functionality that manipulates the clipboard in the browser.
I'm not sure, but I expect that it's the same sort of thing that motivates the inclusion of the ability to enable page content obfuscation schemes that -say- scramble a page's plaintext, but use CSS styles and JS voodoo to make it appear like the page contains only comprehensible text.
I expect that -when using such a scheme-, you'd need to be able to modify what is being tossed on to the clipboard, as -I expect that- the inbuilt selection tool will pick up your garbage data as well as the intended text. [0]
Edit: To be a little more practical, you could (for instance) use the ability to modify the contents of a clipboard to -say- create custom representations of your web application data formats and allow relatively easy transfer between instances of the software.
[0] Yes, I do recognize that allowing copy and paste kinda defeats the purpose of this scheme, but the scheme is something that I've seen in the wild.
While this may not be a huge issue in practice, I have no idea what motivates the inclusion of functionality that manipulates the clipboard in the browser. I don't really think that the analogies of anyone swerving on the highway or someone poisoning your pizza apply. It's more like your seat belts were deliberately removed, or someone put arsenic right next to the pizza box just in case anyone would want to poison you.