When adding a related object (e.g. adding a task to a diff) a popup with a search field pops up.
The search result does only contains results that start with the given search term.

So if you have these 3 tasks ...

• Hello World
• World Hello
• Other random thing

... and you type World in the "related object search field" you'll only get World Hello as a result.

It would be useful if the whole title is searched by a "contains" instead of "starts with"