Uhm, is this a glitch, if so how would I go about fixing it.
This is a default setting; you can disable this in the reputation settings in the ACP.
There is a bug in MyBB I reported. You can leave as many reps as you want and the setting doesn't matter. Those in the HF circle are aware of this.
The setting works as expected for me, it just updates the rating, doesn't add a new one. Post ratings are unaffected, which the setting description explains.