[GeoffR]

The synopsis bug is fixed in the sense that the font size is now what Kobo intended it to be, but here is a patch to change the font size to something different:

Firmware 3.8.0 (add to libnickel.so.1.0.0.patch):

Spoiler:

<Patch>
patch_name = `Custom synopsis font size`
patch_enable = `yes`
#
# Touch/Mini example (20px --> 25px)
replace_string = C6118E, `2\x000`, `2\x005`
# Glo/Aura example (23px --> 30px)
replace_string = C305AA, `2\x003`, `3\x000`
# AuraHD/H2O example (29px --> 36px)
replace_string = C305EC, `2\x009`, `3\x006`
</Patch>

(The replacement string is the font size in pixels, but with a "\x00" between the digits. e.g. 30 is written as 3\x000.)