It would be helpful if comment emails were grouped by the product.

• Comment reply email template (tpl_user_comment_reply_note): https://github.com/KDE/ocs-webserver/blob/master/sql_code/20160921_add_mail_template_comment_reply.sql
• The owner email template's SQL (tpl_user_comment_note) was not commited to the repo it seems.

I'm 90% certain that email subjects support variables.

• getSubject https://github.com/KDE/ocs-webserver/blob/master/application/modules/default/plugins/SendMail.php#L636
• buildBodyHtml() > replaceVars() is similar https://github.com/KDE/ocs-webserver/blob/master/application/modules/default/plugins/SendMail.php#L594

It's been a while since I wrote SQL but I think it would go something like this?

UPDATE
	`mail_template`
SET
	`subject` = '[%product_title%] You received a new reply to your comment',
	`changed_at` = '2018-11-16 23:59:59'
WHERE (
	`name` = 'tpl_user_comment_reply_note';

UPDATE
	`mail_template`
SET
	`subject` = '[%product_title%] You Received A New Comment',
	`changed_at` = '2018-11-16 23:59:59'
WHERE (
	`name` = 'tpl_user_comment_note';