Can someone please explain this misbehavior?

[A B]

SET `collation_connection` = 'utf8_bin';
SET @wrong = CONVERT(CAST(0xD187D0B5D180D0BDD18BD0B9 AS CHAR) USING 'cp1251') COLLATE 'cp1251_general_ci';
SET @right = CONVERT(CAST(0xD187D191D180D0BDD18BD0B9 AS CHAR) USING 'cp1251') COLLATE 'cp1251_general_ci';
SELECT @wrong AS `wrong`, @right AS `right`,
IF(@wrong = @right, 'Bogus comparison', 'Right is right') AS `equality`;


versus

SET `collation_connection` = 'utf8_bin';
SET @wrong = CONVERT(CAST(0xD187D0B5D180D0BDD18BD0B9 AS CHAR) USING 'utf8') COLLATE 'utf8_general_ci';
SET @right = CONVERT(CAST(0xD187D191D180D0BDD18BD0B9 AS CHAR) USING 'utf8') COLLATE 'utf8_general_ci';
SELECT @wrong AS `wrong`, @right AS `right`,
IF(@wrong = @right, 'Bogus comparison', 'Right is right') AS `equality`,
@@collation_connection AS `collation`;

SET `collation_connection` = 'utf8_bin';
SET @wrong = CONVERT(CAST(0xD187D0B5D180D0BDD18BD0B9 AS CHAR) USING 'utf8') COLLATE 'utf8_unicode_ci';
SET @right = CONVERT(CAST(0xD187D191D180D0BDD18BD0B9 AS CHAR) USING 'utf8') COLLATE 'utf8_unicode_ci';
SELECT @wrong AS `wrong`, @right AS `right`,
IF(@wrong = @right, 'Bogus comparison', 'Right is right') AS `equality`,
@@collation_connection AS `collation`;