It may be possible to re-use the code we have for the feedback form to detect the browser platform and take the appropriate action.

Our currently supported platforms are listed here:
http://www.mediawiki.org/wiki/Article_feedback/Version_5/Feature_Requirements#Platforms

At Howie's recommendation, we would like to add one more request for this ticket, as well as clarify how the UI should behave for unsupported platforms.

We would like to display a general disclaimer message for all users, even if they are using platforms we already support:

"This is a prototype, not a final product. Key features are still in development."

If they are using an unsupported platform, this default message would be replaced by the message originally proposed above, as so:

"Sorry, your browser is not supported by this prototype. For a better
experience, please use a different browser."

In both cases, this message would be shown in dark gray text, medium size font, in the same place where we had our previous prototype message (below the title and above the filtering/sorting toolbar).

These messages would appear on both the article page and the central feedback page, as well as their permalink pages.

However, in the case of unsupported platforms, we would NOT show the contents of the feedback page at all below the message, only show the message next to the existing chrome for Wikipedia, at the top of a blank page.

This decision to not show anything for unsupported platforms was reached after we viewed how bad the user interface looks on IE7 (see attached screenshot).

Created attachment 10636
Article Feedback Page on IE7 (with editor tools)

Attached:

Code on Gerrit: https://gerrit.wikimedia.org/r/#/c/8729/