Many bots rely on the version of MediaWiki engine. But they need to make additional request to Special:Version each time they start. For bots involked by cron, recursive bots etc. that causes a large number of unneeded requests to servers. More serious problem is that the format of Special:Version may change as the format of any other pages, and bot won't be able to handle this.
I suggest doing a very simple thing. Let's add a variable, say 'wgMWVersion', to each page, into the block where we define wgScript, wgServer etc. for javascripts.
I'm setting priority to High because it would be possible to write bots fully compatible with older version of MediaWiki only when this feature will be enabled, and only for versions where it is enabled. Don't think that it's hard to implement this, but we need that feature right now.
Thank you.
Version: unspecified
Severity: enhancement