can a broker make users portfolio public if user gives the permission to do so?
Any reason/benefits of making this public?
This is regulatorily grey currently. The issue is can this portfolio in some form construe to be investment advisory if other people start following it. If it is for free it is maybe okay, but if users have to pay to see the portfolio, then it comes under RIA/RA regulations. So yeah grey.
Check this post I had written sometime back
How do media get hold of Rakesh Jhunjhunwala portfolio?
If you are a shareholder you can write to RTA (which maintains the shareholding list of companies) or the company itself and ask for complete shareholding list.
All listed companies declare anyone holding more than 1% in their quarterly filing with the exchange.
By the way you can also download the entire shareholding for any public or private limited company from the MCA (updated once a year).
The public information on shareholding that you see for RJ and others is typically sourced from the above three sources.