Thats to do with phpBB. The forum read setting is changed when you visit the forum and not when you read all the theads in it. All the threads should still appear unread.
MOD Name: Keep unread flagsAuthor: Ptirhiik - RPGnet-frMOD Description: This mod keeps the unread flag active until the topic is readen. It also activate the new post feature for guests.Disclaimer: This MOD has not been Validated by the MOD Team. The MOD has been tested for functionality only. For more information see this topic. However, the author has proven to be trustworthy.MOD Version: 1.0.0Installation Level: EasyInstallation Time: ~ 20 MinutesDownload File: mod-keep_unread.zipFile Size: 25032 Bytes