The deletion of content from a wiki page can be either a good thing or a bad thing depending on the nature of the content and the intent of the deleter.
If content is deleted by accident or for malicious reasons then that is a bad thing and one should expect to have the deletions reverted to the original content. It may be difficult to determine motivation for some of these deletions but if the effect is to remove or replace good content with bad content or no content then one should expect to have the deletion reverted.
Link spam should be deleted wherever found.
If content is deleted as part of a refactoring process that actually improves or clarifies the content then that is a good thing and should be considered a constructive change.