I want to stay with the existing WP core Comments and enable the use of full featured rich text editor in both the front end and the back end. I don’t use the Guttenberg editor. I’d like to be able to add WP core media and galleries, Shortcodes, and third party photo gallery or album objects.
I’ve looked at a couple of plugins, and there doesn’t seem to be any that support any of the features you requested.
I’m not sure when WP Edit plugin stopped working with comments – you should ask theme. Josh is usually very responsive.
But you’ve uncovered an interesting thing about the comment input field that got changed sometime – maybe with WP 4.0. Weaver Xtreme Plus has an option to show “HTML tags available for your comment”. The comment field STILL supports some very basic HTML:
HTML tags allowed in your comment: <a href=”” title=””> <abbr title=””> <acronym title=””> <b> <blockquote cite=””> <cite> <code> <del datetime=””> <em> <i> <q cite=””> <s> <strike> <strong>
Apparently the Weaver Xtreme Plus option to enable that info has been non-operational for a long time. I fixed it by having the theme add the info message back if the option is checked. Seems so strange that WP kept the capability, but doesn’t document it anywhere. Really strange.
As you can see, bbPress does allow editing in replies. We are using WP Edit to enhance the basic Tiny MCE editor commands. Note that Tiny MCE is still a core component of WP, it is just used differently. Previously, that is what the Classic Editor was, and still is with the Classic Editor Plugin. And it is what bbPress still uses.
One of the options for fancy commenting is to use something like Discus or another discussion service.