Wikilinking a label with the ′ symbol in it, represented either by ′ or ′, will freeze the Wikilinking function in the Visual Editor.
- Go to en:GC skew and edit with Visual Editor
- Wikilink the text 5′ to Directionality (molecular biology)
- The Wikilinking feature will freeze and the page will have to be reloaded and changes restored for you to continue editing (screenshot of the 'freeze' below)
Browser: Version 76.0.3809.132 (Official Build) (64-bit)
Note: I reproduced this on https://test2.wikipedia.org too