In the market etc, if you were selling a lot of stuff you can format numbers, for example, if i was to sell a sword for 20million i could put it on the market place for 20,000,000 and it would work.
Doing this in a trade doesn't work. The trade sends (takes the 5k gold for sending it) but it comes through as an empty trade. I found this out last night when doing my quiz when everyone was complaining that empty trades were coming through. Number formatting should be consistent across the site.