yes, this is possible, please follow the steps below:

1. Navigate to Dashboard > Comments > Forms admin page, edit the "Default form" 

2. In "Comment form header text" field, enter the expression you'd prefer with the <br> tag

example here:

Welcome.<br>
Please leave your reply here.

Delete all caches and check again:  

3210

More info here: https://wpdiscuz.com/docs/wpdiscuz-documentation/getting-started/custom-comment-form/comment-form-settings/#comment_form_header_text

Does anybody know if it's possible to enter multiple lines in "Phrases" or to replace the "Leave Reply" title? E.g. I want to create something like this:

Welcome.
Please leave your reply here.

Thank you.