初心者による質問フォーラム

> このタグを, 投稿者が手動でつけることなく自動で付与することは可能でしょうか?

不可能ではないと思います。

もしかしたら、以下のプログラム修正でご希望の動きに近くなるのではないでしょうか。

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Moodleバージョン:
3.7.3 (Build: 20191111)

修正対象プログラム:
config.php

修正箇所:
28行目

[ 修正前 ]
require_once(__DIR__ . '/lib/setup.php');

// Some servers may need a special rewrite rule to work around internal path length limitations:
// RewriteRule (^.*/theme/yui_combo\.php)(/.*) $1?file=$2

// There is no php closing tag in this file,
// it is intentional because it prevents trailing whitespace problems!

[ 修正後 (例) ]
require_once(__DIR__ . '/lib/setup.php');

$CFG->forum_post_tags = array (
    'English001' => 'E001',
    'English002' => 'E002',
    '日本語001' => '日001',
    '日本語002' => '日002',
);

// Some servers may need a special rewrite rule to work around internal path length limitations:
// RewriteRule (^.*/theme/yui_combo\.php)(/.*) $1?file=$2

// There is no php closing tag in this file,
// it is intentional because it prevents trailing whitespace problems!

------------------------------------------------

修正対象プログラム:
mod/forum/lib.php

修正箇所:
3110行目

[ 修正前 ]
function forum_add_new_post($post, $mform, $unused = null) {
    global $USER, $DB;


[ 修正後 ]
function forum_add_new_post($post, $mform, $unused = null) {
    global $USER, $CFG, $DB;

-------------

修正箇所:
3142行目

[ 修正前 ]
    if (!isset($post->mailnow)) {
        $post->mailnow    = 0;
    }

    $post->id = $DB->insert_record("forum_posts", $post);

[ 修正後 ]
    if (!isset($post->mailnow)) {
        $post->mailnow    = 0;
    }

    $default_tags = $CFG->forum_post_tags;

    foreach ($default_tags as $key=>$val) {
        $pos = 0;
        if (function_exists('mb_strpos')) {
            $pos = mb_strpos($post->message, $key);
        } else {
            $pos = strpos($post->message, $key);
        }
        if ($pos > 0) {
            $post->tags[] = $val;
        };
    }

    $post->id = $DB->insert_record("forum_posts", $post);

-------------

修正箇所:
3292行目

[ 修正前 ]
    $discussion->firstpost    = $post->id;
    $discussion->timemodified = $timenow;
    $discussion->usermodified = $post->userid;
    $discussion->userid       = $userid;
    $discussion->assessed     = 0;

    $post->discussion = $DB->insert_record("forum_discussions", $discussion);

[ 修正後 ]
    $discussion->firstpost    = $post->id;
    $discussion->timemodified = $timenow;
    $discussion->usermodified = $post->userid;
    $discussion->userid       = $userid;
    $discussion->assessed     = 0;

    $default_tags = $CFG->forum_post_tags;

    foreach ($default_tags as $key=>$val) {
        $pos = 0;
        if (function_exists('mb_strpos')) {
            $pos = mb_strpos($discussion->message, $key);
        } else {
            $pos = strpos($discussion->message, $key);
        }
        if ($pos > 0) {
            $discussion->tags[] = $val;
        };
    }

    $post->discussion = $DB->insert_record("forum_discussions", $discussion);
------------------------------------------------