That's interesting ..... the best guy to opine would be Jim.

But logically ....especially since you alluded to the fact that most of these Options are NEVER exercised .....

it really shouldn't impact the underlying should it? Because its a derivative to begin with. The QUOTE 'lots of people buying in, broadly across the market' ENDQUOTE if its based on really Index/ETF/Stocks volume - its actual buying - not Derivatives

What's more important is THEN THE OTHER SIDE - ie the people who are writing the calls.

Since Call Writing is marginally bearish - which means the so called "Smart Money" or institutional investors are selling a bit into the rally.

QUOTE : social dynamics in social media to ensure people are actually placing the trades they claim to be placing: 'proof or ban!'. ENDQUOTE

This is BANG ON - influence culture --- People are advertising such BETS - which obviously can influence people ie Retail buyers.

QUOTE: delta-hedging of short-term, highly geared call options should get reversed if the calls are sold back to the MM : ENDQUOTE

It actually really doesn't matter all that much to Delta-Hedgers - they have to re-balance continuously any case - So someone selling it back to them is ie the expected %age built into their strategy.

For them the net objective ( especially in a dividend paying portfolio etc) - is that whether they were able to protect the underlying ownership over the period while offsetting the cost of writing the options against any expected cash payouts from the portfolio. Its typically net negative - ie there's ALWAYS cost of hedging -- but if they expect the portfolio to say appreciate at 7-10% CAGR while they have promised their clients 5-6% they can allocate about 1% to the Hedging program

NET MSG:
Derivative volume doesnt' impact Underlying volume - at least Directly. Sentiment - different matter altogether.

Best