Tag wiki excerpts are for quick plain text descriptions for:
- when the tag should be added to a question
- what other tag might be better, or
- a cursory note on what it represents.
When it starts to become a launch pad for other sites or pages to check out, it's time to dial it back.
Adding in the ability to format, link or imageificate the excerpt veers it into a canyon of oil slicked souls and renders it more promotional than information purposed for the community.
The rest of the tag wiki is open slather for links and other resources. A better place to grasp the sides of and pull it apart to allow better putting one's head up the tag's world of understanding and learning.