Add a strikethrough button in comments editor and wiki (BB-14657)

Issue #11913 open
Theodora Boudale
staff created an issue

Strikethrough is currently supported in the comments editor and wiki with the use of ~~. Without a strikethrough button in the comment editor/wiki, users are not aware of this. It would be useful to have a strikethrough button in the comment editor (Issues & Commits) and wiki.