I think it's pretty common for people (myself included) to name their capture file `capture.org` file, and currently this rule matches it, so if you open capture.org, your end up with it opened in a popup (I believe it wasn't intended?). My fix makes it so it matches only capture buffers (they've got name like `CAPTURE-filename.org`). I believe there shouldn't be any unanticipated consequences of the change?
As far as I understand, the problem is that in elisp, regexes are case insensitive by default, and the sensitivity is controlled by a [variable](http://ergoemacs.org/emacs/emacs_regex.html), so I struggle to see what's the proper way to control it (especially considering the window manipulation happens in `window.el`). If you know of a way to deal with this, happy to implement and update my pull request!
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