When commenting a document in Writer, the shortcut for adding a comment is Ctrl+Alt+C as documented on https://help.libreoffice.org/Common/Comment_1(*).
However, I didn’t find the shortcut to reply to a comment. Acording to the help page, the “Reply” command is available in the context menu of a comment box (when replying a comment of a different author). No shortcut is mentioned in the help, but I suspect a shortcut does exist because when typing comments on my notebook, I got many “reply box” opened just while typing. It was probably triggered by some palm-pressing on the trackpad. Only, I was not able to willingly reproduce this.
Does anybody now such a “reply comment” shortcut ?
(*) for some odd reason, there are two help pages on comments: Comment - LibreOffice Help (well detailed) and Comment - LibreOffice Help (much less detailed). Maybe those should be merged?