Both GitHub and GitLab have built in wiki systems that support Markdown. They also support editing them in a proper editor and using git for revision control.

Both GitHub and GitLab have built in wiki systems that support Markdown. They also support editing them in a proper editor and using git for revision control. That said, these solutions are probably geared more towards developers, whereas in a conventional organization, many people (i.e. business folk) usually prefer a browser based solution that provides a similar experience to that of a word processor. I never liked Confluence, but seeing as the Atlassian suite has become the de-facto industry standard, it's hard to beat its integration advantages with JIRA and such. Better a sucky single source of truth than a disparate array of wonderful solutions. Also I think the latest versions with the UI lift are pretty good (and they support Markdown finally).