I'm building a theme off the back of Luma. I'm mainly doing a few colour changes and moving a few elements around.
When I override the following, it removes the 'Sign In' link from the header:
Magento_Theme/layout/default.xml
Another weird behaviour is:
If I take out my overriding default.xml, redeploy the website (flush the cache etc), the link comes back, then when I put my default.xml back in and redeploy, the link stays until I flush the cache, it then disappears.