10-hinting-slight.conf, 11-lcdfilter-default.conf and 30-metric-aliases.conf definitely weren't there before, and adding them made fonts look wrong. Other people aren't complaining because they just accept the default font rendering. So they already have these files and don't notice when they are re-added.
Today it happened again, after an update of the following packages:
2016-08-19 12:48:03 upgrade libgcrypt11- dev:amd64 1.5.3-2ubuntu4.3 1.5.3-2ubuntu4.4 2~ubuntu14. 04.1 amd64 2.11.0-0ubuntu4.1 2.11.0-0ubuntu4.2 dev:amd64 2.11.0-0ubuntu4.1 2.11.0-0ubuntu4.2 config: all 2.11.0-0ubuntu4.1 2.11.0-0ubuntu4.2 chrome- beta:amd64 53.0.2785.57-1 53.0.2785.70-1 g1b9f164- 1ubuntu2. 1 1.1.8-1ubuntu1~ 14.04.1 runtime: amd64 1.1.6-20- g1b9f164- 1ubuntu2. 1 1.1.8-1ubuntu1~ 14.04.1 g1b9f164- 1ubuntu2. 1 1.1.8-1ubuntu1~ 14.04.1 dfsg0-2~ 14.04.1 6.6-0ubuntu0. 14.04.1 7u111-2. 6.7-0ubuntu0. 14.04.3 7-jre-jamvm: amd64 7u101-2. 6.6-0ubuntu0. 14.04.1 7u111-2. 6.7-0ubuntu0. 14.04.3 7-jre-headless: amd64 7u101-2. 6.6-0ubuntu0. 14.04.1 7u111-2. 6.7-0ubuntu0. 14.04.3 :amd64 41.0.2315.0 41.0.2323.0 20130517. git978d5d8- 1 1.0.15+ r35.1~ubuntu14. 04.1 manager- core:all 1:0.196.14 1:0.196.19 update- manager: all 1:0.196.14 1:0.196.19 notifier: amd64 0.154.1ubuntu1 0.154.1ubuntu2 notifier- common: all 0.154.1ubuntu1 0.154.1ubuntu2 git20131202- 1 0.0.60+ r1683.6. 20160813~ ubuntu14. 04.1 client: amd64 1:6.6p1-2ubuntu2.7 1:6.6p1-2ubuntu2.8 3~ubuntu14. 04.1 nightly: amd64 20160811T205250 .gitaf338f3- 1468.1 20160818T221323 .git37bc956- 1478.1 gnome:amd64 1:6.6p1-2ubuntu2.7 1:6.6p1-2ubuntu2.8
2016-08-19 12:48:03 upgrade libgcrypt11:i386 1.5.3-2ubuntu4.3 1.5.3-2ubuntu4.4
2016-08-19 12:48:03 upgrade libgcrypt11:amd64 1.5.3-2ubuntu4.3 1.5.3-2ubuntu4.4
2016-08-19 12:48:03 upgrade eq10q:amd64 1.2-2 2.0+r136.
2016-08-19 12:48:04 upgrade libfontconfig1:i386 2.11.0-0ubuntu4.1 2.11.0-0ubuntu4.2
2016-08-19 12:48:04 upgrade libfontconfig1:
2016-08-19 12:48:04 upgrade libfontconfig1-
2016-08-19 12:48:05 upgrade fontconfig-
2016-08-19 12:48:05 upgrade google-
2016-08-19 12:48:09 upgrade libmtp-common:all 1.1.6-20-
2016-08-19 12:48:09 upgrade libmtp-
2016-08-19 12:48:10 upgrade libmtp9:amd64 1.1.6-20-
2016-08-19 12:48:10 upgrade libserd-0-0:amd64 0.18.2~dfsg0-2 0.22.0~
2016-08-19 12:48:10 upgrade openjdk-7-jre:amd64 7u101-2.
2016-08-19 12:48:10 upgrade icedtea-
2016-08-19 12:48:11 upgrade openjdk-
2016-08-19 12:48:14 upgrade opera-developer
2016-08-19 12:48:18 upgrade swh-lv2:amd64 1.0.15+
2016-08-19 12:48:18 upgrade update-manager:all 1:0.196.14 1:0.196.19
2016-08-19 12:48:18 upgrade update-
2016-08-19 12:48:19 upgrade python3-
2016-08-19 12:48:19 upgrade update-
2016-08-19 12:48:19 upgrade update-
2016-08-19 12:48:19 upgrade calf-plugins:amd64 0.0.19+
2016-08-19 12:48:21 upgrade gpgv:amd64 1.4.16-1ubuntu2.3 1.4.16-1ubuntu2.4
2016-08-19 12:48:31 upgrade gnupg:amd64 1.4.16-1ubuntu2.3 1.4.16-1ubuntu2.4
2016-08-19 12:48:33 upgrade openssh-
2016-08-19 12:48:33 upgrade a2jmidid:amd64 8~dfsg0-1 8+r170.
2016-08-19 12:48:33 upgrade fontconfig:amd64 2.11.0-0ubuntu4.1 2.11.0-0ubuntu4.2
2016-08-19 12:48:34 upgrade openscad-
2016-08-19 12:48:34 upgrade ssh-askpass-
2016-08-19 12:48:35 upgrade guitarix:amd64 0.28.2-4 0.34.0-0~14.04.2
The following links were added or updated: avail/10- antialias. conf avail/10- hinting. conf slight. conf -> ../conf. avail/10- hinting- slight. conf bitmap- fonts.conf -> ../conf. avail/10- scale-bitmap- fonts.conf default. conf -> ../conf. avail/11- lcdfilter- default. conf small-vera. conf -> ../conf. avail/20- unhint- small-vera. conf aliases. conf -> ../conf. avail/30- metric- aliases. conf avail/30- urw-aliases. conf avail/40- nonlatin. conf avail/45- latin.conf avail/49- sansserif. conf avail/50- user.conf avail/51- local.conf avail/60- latin.conf persian. conf -> ../conf. avail/65- fonts-persian. conf avail/65- nonlatin. conf avail/69- unifont. conf avail/70- no-bitmaps. conf avail/80- delicious. conf avail/90- synthetic. conf
drwxr-xr-x 2 root root 4,0K 2016-08-19 12:48:43.591866038 +0200 ./
drwxr-xr-x 5 root root 4,0K 2016-08-19 12:48:43.584866038 +0200 ../
lrwxrwxrwx 1 root root 31 2016-08-16 21:18:00.000000000 +0200 10-antialias.conf -> ../conf.
lrwxrwxrwx 1 root root 29 2016-08-16 21:18:00.000000000 +0200 10-hinting.conf -> ../conf.
lrwxrwxrwx 1 root root 36 2016-08-16 21:18:00.000000000 +0200 10-hinting-
lrwxrwxrwx 1 root root 40 2016-08-16 21:18:00.000000000 +0200 10-scale-
lrwxrwxrwx 1 root root 39 2016-08-16 21:18:00.000000000 +0200 11-lcdfilter-
lrwxrwxrwx 1 root root 39 2016-08-16 21:18:00.000000000 +0200 20-unhint-
lrwxrwxrwx 1 root root 36 2016-08-16 21:18:00.000000000 +0200 30-metric-
lrwxrwxrwx 1 root root 33 2016-08-16 21:18:00.000000000 +0200 30-urw-aliases.conf -> ../conf.
lrwxrwxrwx 1 root root 30 2016-08-16 21:18:00.000000000 +0200 40-nonlatin.conf -> ../conf.
lrwxrwxrwx 1 root root 27 2016-08-16 21:18:00.000000000 +0200 45-latin.conf -> ../conf.
lrwxrwxrwx 1 root root 31 2016-08-16 21:18:00.000000000 +0200 49-sansserif.conf -> ../conf.
lrwxrwxrwx 1 root root 26 2016-08-16 21:18:00.000000000 +0200 50-user.conf -> ../conf.
lrwxrwxrwx 1 root root 27 2016-08-16 21:18:00.000000000 +0200 51-local.conf -> ../conf.
lrwxrwxrwx 1 root root 27 2016-08-16 21:18:00.000000000 +0200 60-latin.conf -> ../conf.
lrwxrwxrwx 1 root root 35 2016-08-16 21:18:00.000000000 +0200 65-fonts-
lrwxrwxrwx 1 root root 30 2016-08-16 21:18:00.000000000 +0200 65-nonlatin.conf -> ../conf.
lrwxrwxrwx 1 root root 29 2016-08-16 21:18:00.000000000 +0200 69-unifont.conf -> ../conf.
lrwxrwxrwx 1 root root 32 2016-08-16 21:18:00.000000000 +0200 70-no-bitmaps.conf -> ../conf.
lrwxrwxrwx 1 root root 31 2016-08-16 21:18:00.000000000 +0200 80-delicious.conf -> ../conf.
lrwxrwxrwx 1 root root 31 2016-08-16 21:18:00.000000000 +0200 90-synthetic.conf -> ../conf.
10-hinting- slight. conf, 11-lcdfilter- default. conf and 30-metric- aliases. conf definitely weren't there before, and adding them made fonts look wrong. Other people aren't complaining because they just accept the default font rendering. So they already have these files and don't notice when they are re-added.