I tracked this down to a bug in emacs, which happens only when indirect
buffers are cloned. Reported as bug#53294 with a patch.

On Thu, Jan 13, 2022 at 9:51 PM Andrew Hyatt <ahyatt@gmail.com> wrote:

>
> Hi all,
>
> I've been having an odd problem where if I try to change my text
> scale on my org capture buffers, the scale keeps increasing, and
> increases the scale on the parent of the indirect org-capture
> buffer, on each capture.
>
> I'm using org-mode 9.5, emacs 29.0.50.
>
> Debugging into the issue, I realized I can only reproduce this if
> the org-mode buffer has variable-pitch-mode on.
>
> Here's a short repro that works on emacs -Q (of course, you may
> want to change the path):
>
> (require 'face-remap) (defun ash/big-font ()
>   "Creates a font that is big enough for about 20 lines of text."
>   (interactive) (let ((text-scale-mode-amount (/ (frame-height)
>   20)))
>     (text-scale-mode 1)))
>
> (require 'org-capture) (add-hook 'org-capture-mode-hook
> #'ash/big-font) (setq org-capture-templates '(("c" "Capture" entry
> (file "~/Desktop/test.org") nil))) (find-file
> "~/Desktop/test.org") (variable-pitch-mode 1)
>
> After evaluating this, every time you call org-capture, the text
> size will increase, until the text size is so large emacs crashes!
>
> I have also tried to reproduce this without org-mode, just using
> indirect buffers, but can't do it.  Something that org-mode is
> doing is causing this, but org-capture is complicated enough that
> I can't really see what it could be.  I can and will continue
> looking into this, but I'm curious if anyone might have a clue as
> to what is going wrong here.
>