non-ASCII characters are displayed in html encoding in plain-text email template from batched notifications feature

Summary

Issue Summaries with non-ASCII characters are displayed in html encoding in Batched notification plain-text email template

Steps to Reproduce

1. Enable batched notifications
2. Edit user profile to enable plain text email notifications (HTML is on by default)
3. Create an issue with non-ascii characters in the summary e.g. asscented characters like ä

Expected Results

Ascented characters are displayed properly and consistently across the email content

Actual Results

The issue summary has non-ascii characters html encoded in a specific part of the email template as illustrated below:

Workaround

1. Have affected users switch to HTML email notifications from their user profile
2. Disable batched notifications feature.