I think it will be usefull if you have russian language pack on your osc to avoid ??????? instead of cyrilic chars in the tags. When install and tune this mod, coding of following tables in DB should be changed for utf8_general_ci by executing type_any_name.sql file with following content:
ALTER TABLE `headertags` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_cache` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_cache` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_default` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_default` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_keywords` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_keywords` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_search` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_search` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_silo` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `headertags_silo` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
just put above code in blank plain text file and save with any name with extention *.sql than go to phpMyAdmin-your DB-import-choose this sql file and OK, tables will be recoded.
Otherwise cyrilic characters is displayed as ????????????? in tags.
PS All mentioned probed by me with 3.2.8 HeaderTags SEO mod and 2.3.1 release of Oscommerse.
rgrds