How much username information should be available?

The most information that I have seen disclosed is full legal name, national ID number and date of birth on older Bondora contracts. And in the case of a criminal prosecution details of the court and decision.

Zopa have in the past disclosed the court where a borrower was made bankrupt, allowing identification of the consumer unsecured loan borrower from public records.

Ablrate use what I think are unchanging ID numbers on secondary market contracts, allowing tracking of deals by individuals, in great detail if crowdsourced information merging across many different buyers and sellers was done. If you were to mention even once here that you did a particular deal your transactions might be trackable to your account here. Not just by the platform but by other customers. The ID numbers appear to be account numbers that are sequentially allocated, disclosing rough time of account creation and facilitating identification. The actual loan contracts give full lender legal name but those don't go to the buyer/seller in secondary market trades. So borrowers could say see if any famous people had lent them money.

Starring can make it harder to track individuals by increasing the number of possible individuals who could have done a deal, if sufficient ambiguity is provided. So a platform might use enough stars to ensure say 100 possible matches in the actual active account name database.

Whether a platform would have a valid business purpose in facilitating tracking of all deals done by an individual is something for the Information Commissioner and/or FCA to resolve, but not is what I would expect the opinion to be if the IC was asked. The IC has in the past ruled that a forum ID is an identifiable individual so identifying all deals by kaya would suffice as a possible concern even without knowing who kaya is outside the context here where kaya is a known individual with reputation here.

The trouble with usernames is that people recycle them heavily and if your username is unique on the internet then typing it into Google often reveals a lot about your online person. It takes some care to ensure you split your usernames on one kind of website from usernames on another type of site lest someone make the link between the two and find out more about you than you perhaps intended

I much prefer it to show as A****e so you cannot tell my username. 

It does seem a bit too much information the way FS do it, I am not even sure how to change my username on the site (if I accidentally used my full name or username would identify me from google). It would not be hard to write a scraper that collated all the investments across all loans and worked out how much people had invested. If they just mapped every user to an automatically generated username/id it would stop you from being able to identify users directly but still give interesting info on investments.

Property Moose seem to give you easy control over what you share/ don't share. I like how they 'gamify' it a little by letting you compare your capital growth % against others!

Sorry about that, can't put that in now. We could always run it again, but as you infer, it is really a trivial matter anyway.

Platforms could always just provide a simple additional opt in/out Privacy setting allowing a user to control whether their bids/investments are fully visible to other investors or hidden and invisible to other investors.

This would be the best of both worlds as it gives users the choice over whether they remain anonymous or not!