Jetpack and Jetpack Comments do not make any changes to the way comments are displayed on your site.
By default, WordPress doesn’t allow embeds in comments, unless you have added a plugin like oEmbed in Comments. Could you check if this plugin is active on your site?
If it’s not, you will want to check each plugin installed on your site in order to find out which one affects the way comments are displayed.
(@lorenzone92)
11 years, 2 months ago
How can I disable autoembed (for example: YouTube) on comments?
http://wordpress.org/extend/plugins/jetpack/