Fun fact 
- The insert date feature is part of the Local Dates plugin, which comes bundled with Discourse (along with some others like Discobot, Hide Details, Chat, and so on). Unfortunately, with it being a plugin, safe mode no_plugins would disable it just like other optionally installed plugins. 
There is an option to enter safe mode with only non-official plugins disabled, along with disabling themes and theme components, which might be worth a shot?
