I can't speak for Charles, of course, but actually, phpBB doesn't have the function; never has and at this point I guess it never will. People on the phpBB "Extension Forums" have been asking for and talking about it for a decade. Everything that's ever been available (to my knowledge) has been a third-party add-on that would have to be trusted, hope its codding is kept current, and then have to be managed/updated separately. And none of the handful that have appeared have lasted very long. One was called "Post Love" but it's been abandoned for a few years now. https://www.phpbb.com/community/viewtopic.php?t=2246576 There's another one out of Russia that was never very popular and was last updated over a year ago, for phpBB v3.3.0; current version is v3.3.4 released last May. https://www.phpbb.com/customise/db/exte ... r_posts_2/
Not phpBB, but I've had CMS websites in the past breached solely due to vulnerabilities opened up by third-party plugins. I personally avoid all but commercial, for-fee, popular add-ons produced by known-stable companies with solid reputations. So it doesn't surprise me that we don't have what on the surface seems like a simple, common feature found everywhere from Reddit to Facebook.