Why am I getting website code when I copy and clip as RTF?

I’m picking up code when I copy chunks of webpages. Here’s an example of a commenter from a webpage I copied. The bold parts are what shouldn’t be there. Is this the webmaster’s fault? It’s been happening for the last three days whenever I clip using Shift+Command +)

Here’s another example of what happens after the webpage title. I have to cull every entry of this stuff:

The text snippet is actually provided by the source application, probably a browser, and stored by DEVONthink without any modifications.