Azure DevOps includes a Wiki feature for all projects. The wiki content is stored as a git repository, with a .md markdown file for every page. You can clone the repository and look at how it is organised. All pages in the wiki allow users to submit comments - clearly these must be stored somewhere, but where? They do not appear in the wiki repository.
Unfortunately, we haven't sort it into any history and it only relevant to Wiki page until now. This comment feature is being implement but haven't supported from UI.
As of today, what we provide is view the comments content from UI, or get them from API:
Get https://dev.azure.com/{org name}/{project name}/_apis/wiki/wikis/{wiki name}/pages/{page id}/comments
In fact, the backend data structure has been built, but we haven't provide the corresponding UI to public. So, with above api, you can not only get the comments you want, but also record the modification history of the comments.
Personally, it sounds a good idea about putting comments into source control since it not only records some important conversation about current wiki, also has representation about its development process.
Much recommend you can share your idea here, it is the official forum that our Product Group reviewed.
You can share the suggestion ticket link here, I'm sure I would be the first voter on that. Also, there will have other SO users who view this ticket support that.