The incentive to make best efforts will remain as long as promoter has significant wealth tied to the fortunes of his shareholding. Having a benevolent owner at the helm is necessary, but not sufficient, to ensure management has a long term strategy. It’s not necessary for the owner to run the business themselves, they can always employ capable managers having right values for the job. For the minority shareholders, it is more important to ensure that the owner has integrity, so they wouldn’t try to cheat the minority shareholders in future. The Info Edge promoters do have sufficient holding to act as owner, and this holding represents a significant wealth for them.
Of course promoter has better insight into the business than the average investor. It’s natural to wonder whether promoter buying/selling can be used to make a profitable trading signal. Page and Bajaj Finance are good examples where it worked. But a trading signal must be thoroughly tested to determine if it gives an edge. You must also look at the incidence of deconfirmatory examples. Also, if you decide to use a trading signal, you must use it consistently. You cannot use it sometimes when it support your position, and ignore it otherwise.
I don’t believe promoter buying/selling information obtained from exchange would give any trading edge, as it is easily available information to everyone. Let’s look at Page again, its promoter holding was reduced from 51 to 49 in Mar 2016. Its price in April 2016 was around 12k, and the holding remained constant till June 2018. The price peaked around August 2018 at ~35k. Even after the price fall, the investor/trader is better off ignoring the Mar 2016 stake reduction.
Disc: Invested in Info Edge.