I don't moderate that forum myself, so I don't know the reason why exactly, and once a post is deleted it's deleted, so I can't even see what you had put.
Were you answering by linking to an external website that may be considered to be advertising?
Were you answering by linking to your own blog?
Have you considered that the question you are answering is over 3 months old, so it probably not considered 'active' any more? (In this case I would have posted to tell you it's an old thread and perhaps locked it, but I can't account for what other moderators do) It's not good practice to drag up older threads when there are current ones that need answering. If a person didn't get an answer in reasonable time it's unlikely they'll still be sat there waiting for one.