8 - How do I check if a comment is from original poster?
Actually, before you write any code... D8 automatically adds a 'by-[entity-type]-author'(e.g. by-node-author) class to the &lt;article&gt; tag of each comment, if commenter and author are the same.
This is defined at line 73, in comment.html.twig file(at least this is the case in Bartik theme file), so please take advantage of it :)