If you want to use P as the reply author, be sure to be signed in the Chrome Web Store as P. Please note that P should be a Google account. If you want that certain name be displayed as the post author, set it as your Google Account name. For details see Change your Google Account name & other info
The above because the posts in the Chrome Store, either as an user review or as an reply to an user review are attributed to the Google account used to post them.
If you reply is something important you might want to mention that in the extension description or to include a link to blog post or help article in the Chrome Extension official website.
As of the first week of January 2021, the official document about the Chrome extension developer in the user review system is very scarce:
Apparently the only official doc pointed to developers is a blog post from 2015 (see quote below) which points to Tips for using the Chrome Web Store
From https://blog.chromium.org/2015/10/replying-to-reviews-in-chrome-web-store.html (emphasis mine)
Before replying to user reviews, please read the commenting guidelines to ensure that your use of this feature is compliant with Chrome Web Store policies. Also remember that when posting reviews, your name and Google account will be shown publicly so that prospective users can see that you consistently provide high quality customer support. Head over to your reviews tab and start connecting with users today!