虽然平常用时bright的最高级是brightest，在诗歌里可以用most bright。下面是十七世纪威尔士诗人George Herbert写的一首诗的第一段：

O day most calm, most bright,
The fruit of this, the next world's bud,
Th' indorsement of supreme delight,
Writ by a friend, and with his bloud;
The couch of time; care's balm and bay: 5
The week were dark, but for thy light:
Thy torch doth show the way.

如果到网上查一下，会发现不少英语诗词、歌词都用了most bright。英语是一个很不规范的语言，很多语法规则都有例外。fls网友所说的语法规则是对的，但是这句话正好是个例外。之所以"社会各界没有人发现并加以纠正"，是因为这并不是个真正的错误。