Honestly, two lines just isn't enough. The old server showed the entire annotation on the various pages where it was seen, and I don't particularly recall hearing any complaints about that.
Two lines might not be enough, but showing the entire annotation is not a good idea - see e.g. http://classic.musicbrainz.org/artist/a16e47f5-aa54-47fe-87e4-bb8af91a9fdd.html.
This doesn't really make sense now that we have inline full annotation loading. If someone wants this behaviour explicitly, a user-script is suitable.
After chatting in IRC, I changed my mind - re-opening.
The full annotation should be shown, because its primary content is usually notes from one editor to another, some of which may be important information about things that shouldn't be edited and why they are that way.
Hiding this by default, particularly for new editors who don't use userscripts, is a bad idea.