The problem is that people can have multiple accounts. For example, if I have two accounts one called Hydrix and the other called Onyx. One is ironman, the other is not. Will I get the rank/badge?
If yes; Everyone will make a new ironman just to get that rank/badge
If no; Rank/badge is useless
The example you gave is one of a no forum to game connection or a 1 account, multiple characters connection. Where on any game, have you not had more than 1 account? Ironman and Ultimate Ironman is basically a game mode not a rank, donation ranks can also be handled in that or in an in game rank separate but, having donation grades on the forum makes more sense than Ironman grade. If you are concerned about people just making Ironmen to get a badge and not progressing why not suggest that accounts have active and inactive options where if an account isnt accessed after 2 or so months the active changes to inactive and after a year the account is then moved to a database for inactive users, seeing that someone may come back, sign on then their account is then pushed back to the main user database.