b> Links in the sidebar are not checked for redlinkiness, no. Is there b> any reason they should be?

Just as much reason as any link.

Why make them a special case? of brokenness too.

If they are red then we won't click on them like a boob.

If they are red then we will remember to do something about them, (edit or remove (with "-")) especially as every user sees them on every page!