Yesterday, June 2, 2017, I experienced this same glitch using Safari 10.1.1
1. Open a new post
2. Type words using the Visual editor
3. Highlight the words
4. Click the Visual editor “Insert Link” icon.
5. Highlight disappears
6. I am able to insert the link using the Text editor
Thanks for your help. http://www.seacoastmission.org is the URL.
Best,
Scott