Clicking the 'eye' button, which I assume is the 'read' icon, marks the manga as unread. There's no way to toggle it back. Also, there's no tool tip indicating what the eye icon means. The eye can easily mean 'read' or 'new things to read' imo.
Steps to reproduce:
1. Choose a manga, $MANGA
2. Follow $MANGA
3. Read the last chapter of the $MANGA (I assume this is how you get the eye icon, otherwise, maybe read all of the chapters of the manga)
4. Go to https://mangadex.org/follows
5. $MANGA should have an 'eye' icon
6. Click it
7. Watch it vanish
Steps to reproduce:
1. Choose a manga, $MANGA
2. Follow $MANGA
3. Read the last chapter of the $MANGA (I assume this is how you get the eye icon, otherwise, maybe read all of the chapters of the manga)
4. Go to https://mangadex.org/follows
5. $MANGA should have an 'eye' icon
6. Click it
7. Watch it vanish