the only problem i can foresee is the usual one for projects on savannah - many projects will have the savannah bug tracker enabled and accepting bug reports, even if the maintainers never read it - therefore users submit bug reports and the maintainers never read them
GNU devs do seem to prefer the email workflow; but librejs is not the typical GNU program - it is easy to argue that the mail driven workflow makes it _less_ accessible to the typical users of webby things, most of whom would prefer something more webby, such as the savannah, pagure, or github bug trackers - all of those are currently accepting bug reports for librejs - ive seen it often where users will post bug reports on the webby bug trackers, even if the upstream suggests not to, simply because they accept bug reports and users find it more convenient - so they do it anyways, and those bug reports go unseen by the maintainers so if you do this, i suggest closing the savannah, pagure, and github bug trackers - but it would be better to continue watching them for bug reports in addition to the mailing list - thats how it has been for years - converting the mailing list into a debbugs tracker is not a very significant change unless the savannah, pagure, and github bug trackers are closed, or unless they remain open but are no longer watched - arguably, neither of those options would be an improvement though - unfortunately, to require users to submit bug reports via email is a great way to ensure that you get no bug reports
