With bug 49931 we currently extend link annotations when typing at the end. This makes it very difficult to type plain text after a link at the end of a paragraph.
We should change the logic to stop extending the annotation once a character is added that produces a new wordbreak.
There may be some odd cases as wordbreak logic can depend on more that two characters, e.g. a' has a wordbreak but a's doesn't, so trying to add "'s" to the end of a link label would break after the "'" even though it wouldn't if "'s" was added as one operation.