Wiki linking behavior should be consistent with documentation

• Documentation is being added in !4372 (merged), particularly in wiki.md. These rules need to be approved and merged in.
• Links in the wiki should follow these guidelines, both on the wiki page and the wiki preview page

/cc @brodock @rymai

TODO

• #18019 (closed) Fix wiki linking behaviour
  • !4372 (merged) Document the intended wiki linking behavior
  • !4432 (merged) Have wiki linking behave as per the documentation