We're dealing with a similar problem on Super User.
When I started a clean-up, I reserved destruction only for answers that were
- scored at zero or below,
- not the accepted answer,
- written by users unlikely to come back,
- not the only answer, and
- obviously lacking effort.
In general, we're trying to avoid removing something that someone found helpful. For link-only answers written by users who are still around, I left a comment along these lines:
At the moment, this post is essentially only a link. To make sure the answer remains useful even if the link breaks, please edit it to include the relevant information. (Your answer was discovered in an effort to repair or remove old link-only answers.)
Markdown source for the above:
At the moment, this post is essentially only a link. To make sure the answer remains useful even if the link breaks, please edit it to include the relevant information. (Your answer was discovered in [an effort to repair or remove old link-only answers](https://meta.serverfault.com/q/8567/283572).)
If an accepted (or upvoted) answer is link-only, it should probably be edited rather than destroyed, preferably by the original author. If it's outvoted by an actual answer, though, not much valuable will be lost if it's deleted or converted to comment.