When a group of greater than or less than symbols are repeated together, html_gen.e fails to escape them properly, leading to raw characters in the resulting HTML. Although this does not seem to break anything in most browsers, nor does it appear able to provide the capability to embed raw HTML (as it's not possible to embed text between a less-than and greater-than symbol with this bug to create an HTML tag), this is still a technical violation of the standard.
Example:
4. >>>>>>> From the Geany menu, "Tools", click on "Reload Configuration". <<<<<<<<<<
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