Does Bugzilla support any markup language?

At this moment, Markdown formatting is supported on https://bugzilla.mozilla.org/ based on my own testing just now. There's a small link that says "Markdown styling now supported"

However, Mozilla's bugzilla instance appears to be running one of several Markdown Bugzilla extensions listed on GitHub, since Markdown doesn't seem to be mentioned in the bugzilla code repository.

As for version history, bugzilla.mozilla.org links to documentation indicating they are running Bugzilla 4.2. Markdown was introduced in the Bugzilla 4.5.6 development snapshot, but reverted from 5.0. Then, Markdown support was included in the Bugzilla 5.1.2 documentation.

I can't find current plans. There was discussion here without clarity about what happened:

• https://bugzilla.mozilla.org/show_bug.cgi?id=330707
• https://wiki.mozilla.org/Bugzilla:Markdown

Conclusion

Any given Bugzilla installation may or may not support Markdown right now, but Markdown was designed to be readable, so go ahead and use it. It seems likely it will be rendered as HTML in the near future even if it isn't right now.

Edit: Bugzilla 6.0 will include optional markdown support; it was implemented as a GSoC project in the bug linked in the question. Docs.

Before 6.0, the only thing it supports is the > prefix on lines, which makes them purple and not wrap.