Add pull request title recommendations to CONTRIBUTING.md (mastodon#16247)

Author: Gargron

CONTRIBUTING.md

@@ -24,9 +24,17 @@ You can submit translations via [Crowdin](https://crowdin.com/project/mastodon).
 
 ## Pull requests
 
-Please use clean, concise titles for your pull requests. We use commit squashing, so the final commit in the master branch will carry the title of the pull request.
+**Please use clean, concise titles for your pull requests.** Unless the pull request is about refactoring code, updating dependencies or other internal tasks, assume that the person reading the pull request title is not a programmer or Mastodon developer, but instead a Mastodon user or server administrator, and **try to describe your change or fix from their perspective**. We use commit squashing, so the final commit in the main branch will carry the title of the pull request, and commits from the main branch are fed into the changelog. The changelog is separated into [keepachangelog.com categories](https://keepachangelog.com/en/1.0.0/), and while that spec does not prescribe how the entries ought to be named, for easier sorting, start your pull request titles using one of the verbs "Add", "Change", "Deprecate", "Remove", or "Fix" (present tense).
 
-The smaller the set of changes in the pull request is, the quicker it can be reviewed and merged. Splitting tasks into multiple smaller pull requests is often preferable.
+Example:
+
+|Not ideal|Better|
+|---|----|
+|Fixed NoMethodError in RemovalWorker|Fix nil error when removing statuses caused by race condition|
+
+It is not always possible to phrase every change in such a manner, but it is desired.
+
+**The smaller the set of changes in the pull request is, the quicker it can be reviewed and merged.** Splitting tasks into multiple smaller pull requests is often preferable.
 
 **Pull requests that do not pass automated checks may not be reviewed**. In particular, you need to keep in mind: