A good compost will have enough humic acids in it for bacteria and fungi to use so adding a commercial humic acid preparation is not necessary or may even have a negative effect as was mentioned.
One issue with humic acid products is the extraction method that is used. If the extraction uses a strong acid or base the humic acids are denatured and cannot be used immediately by bacteria and fungi. Dr. Elaine Ingham wrote about this a few months ago in the Compost Teas, The Soil Food Web & Soils Yahoo Group. It can take many months for any denatured humic acids to become bioactive again.
You can ask Kelp4Less for more information on extraction methods that are used in humic acid products they sell but from my experience they are not very forthcoming with technical details.
I would suggest going over to
bioag.com and read about their products. They have a lot of good information on humic and fulvic acids and their extraction methods which do not include chemical extraction with strong acids or bases. Their Ful-Humix soluble powder would be a good choice if you want quality humic/fulvic acid product to experiment with.