Simplify code at a few places

Remove some duplicate checks,
and unnecessary errors.
What you are saying is implemented on our newer (ie. observer and shooter) Annotator branches, which have better support for tracking the anchoring status of annotations, and is actively re-anchoring them when needed. I see no sane reason to start to refactor this part of this legacy branch, since
 * we are going to move away from our fork anyway, and
 * even inside our fork, we have much better branches; any further work on this branch will just cause us more work.

So I only add small, local changes; I don't want to change how it's all wired together.