It most certainly does not ignore pinning. Your pinning was probably wrong. Like, one user had their entire file indented and thus no pins were read because everything was treated as a comment.
You might want to ask in a user support channel for assistance with pinning. ** Changed in: apt (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to apt in Ubuntu. https://bugs.launchpad.net/bugs/1734621 Title: apt ignores pinning in /etc/apt/preferences Status in apt package in Ubuntu: Invalid Bug description: On Ubuntu 17.10 apt ignores pinning set in /etc/apt/preferences. I added the proposed repo and set the pinning for it to 400. Despite this, apt showed everything in proposed as upgradeable. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: apt 1.5.1 ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8 Uname: Linux 4.13.0-17-generic x86_64 ApportVersion: 2.20.7-0ubuntu3.5 Architecture: amd64 CurrentDesktop: GNOME Date: Mon Nov 27 13:12:52 2017 InstallationDate: Installed on 2017-11-27 (0 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20171018) ProcEnviron: LANGUAGE=en_IN:en PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_IN SHELL=/bin/bash SourcePackage: apt UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1734621/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp