Some of the changes in XF 2.1.7 include:
Ensure that some jobs do not attempt to complete or otherwise change state inside a transaction.
Ensure correct URL is used in the bookmark label filter when friendly URLs are not enabled.
Display correct username styling when viewing users linked to an IP.
In alerts and the news feed, ensure the "your post" link in the reaction item is clickable.
Ensure Gravatar rebuild job respects the options sent to it.
Prevent users from deleting their own accounts
Check for guest posts in post reaction items
Ensure login button when viewing a forum as a guest wraps properly.
Only try to hide the global action indicator if it's actually present.
Do not redirect back to the login page after a connected account request
Properly check for tag container inside tagger
Do not escape outbound email test subject phrase
Correctly handle add-ons created with incorrect casing when the namespace already exists.
Add additional wording to make it clear that the rejection reason will be shown to users awaiting approval.
Remove hard-coded height from payment inputs
Add missing phrase for 'could_not_find_subscriber_id_for_this_purchase_request'
Display PHP's memory_limit within server environment report.
Force choice builder to use temporary variable with set tags
Remove Google+ URL from the Google connected account template.
Allow disabling pointer events for nested tooltips
Remove unused parameter when fetching reaction phrase
Update promotion history interface for clarity
Fix post copier attachment regex