Thank you for choosing to use our TOP Table of Contents plugin. We appreciate your support and are sorry to hear that you are experiencing issues.
However, we believe that the problem you have described may not actually be a problem. We have tested the plugin using Bold formatting on our own site and found it to be working perfectly fine, as can be seen on this page: https://insight.boomdevs.com/bold-heading/.
If you are still encountering issues, could you kindly provide us with the URL of your site so that we can conduct further investigations and offer assistance accordingly?
Thank you for your time and cooperation.