The line formatting characters (e.g \t\n\s) are shown for the description's text within the notification emails. Update on 28/06/2018: Values are now within quotes ("...") and it affects the Issue Details View's Tabs and the Webhooks too

noticed that the line formatting is present inside the notification's email for the Description field's change.

We can see \r\n at the start of each lines and depending of the text within this field, other line formatting characters like "/s" or "/t" can also appear within the text. Either HTML or Text formatting is selected for the outgoing email format.

Regarding the wiki markup a feature request is already raised https://jira.atlassian.com/browse/JRACLOUD-31199

Update on 28/06/2018:
This new bug is affecting the description field's values also within the Issue Details View's Activity Tabs, History and within the Webhooks too.
Another thing is the new values are now within quotes (see Activity Tab, History Tab and Webhook Screenshot below).

Activity Tab:

History:

Webhook: