This is an issue in the new ("ooMenu" based) suggester.

Bug 66748 was fixed by removing a broken feature completely. This feature should be reimplemented as it was intended originally. Which is:

1. Add a statement and start searching for a property.
2. Type "Abc".
3. Lets assume the first hit is a property named "Abcdef" with an alias "Abc".
4. This was automatically selected in the old suggester (because the prefix matched). The added suffix was selected so you could continue typing.

This is heavily related to bug 66437 but a separate issue because the selector for properties uses other code that the selector for sitelinks and pages.

Version: master
Severity: normal
Whiteboard: u=dev c=frontend p=0
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=66437