Add dynamic ability to set "Leave a reply" header text (based on post title & no. of comments)

I was just looking at this blog post: https://www.longren.io/add-html-to-the-end-of-every-wordpress-post/#respond

And noticed how the header for the comments section was "One thought on “Add HTML To The End of Every WordPress Post”"

This is great for two reasons:

1. It includes the name of the post - great for reminding the user what they're reading as well as SEO

2. The "One thought" (or I guess in the future "Ten thoughts") part encourages people to take a part in the discussion. Imaging my comment thread has 100 comments, saying "100 thoughts on XXX" is way more appealing than "Leave a reply".

As such, I would love for there to be a way to alter the "Header Text" for a form, either in one of two ways:

1. Shortcodes which I can enter straight into the box on the Edit form page (e.g. [title] for Post title, [comment_qty] for number of comments). E.g. I could use "[comment_qty] thoughts on '[title]'" to get the same style as the link above.

2. Push the 'header_text' or more specifically `getHeaderText()` function through a filter so that I can use add_filter and edit it myself from functions.php

Thanks!