If you add HTML formatting and hyperlinks to a task's Description field, you may lose that formatting when you enable Outlook Sync for your tasks within SharePoint Online, MySite, Task list.
This is by design, because this also syncs Project tasks and because Microsoft Project Professional does not handle HTML. When linking to the Exchange Body property, the sync engine retrieves the text version of the task’ s description. This same behavior is used when synchronizing to your SharePoint, MySite, Tasks list. The Tasks list can hold both SharePoint tasks and Project tasks, therefore we default to using the behavior for Project Professional.
Article ID: 2895493 - Last Review: Jan 13, 2016 - Revision: 1
Microsoft SharePoint Online, Microsoft Project Online