If there is value to supporting <pre> and these others in addition to Markdown's backticks and indent, adding <samp> would provide similar value, both in allowing HTML to be pasted and supported, as well as styling context (such as not attempting to syntax highlight the content).
What benefit would this give over using backticks (sparingly), the existing 4 spaces for code, or the existing
This is the output from using the `pre` tag. The text is smaller and you can't show text inside angled brackets - like ``.
If you use