I fixed it. I opened my 2yo HomePod2 and disconnected the touch panel. Reassembled it (tying the fabric again was tough work, but did it anyhow), and now its working well. No ghost touches, no random Siri activations, no sudden volume max-outs. Absolute fix.
If Apple is reading this post, please note:
"You guys may not acknowledge the issue with your hardware, you may deny paid/good-will repairs (in India you guys tell it cannot be repaired and only can be replaced) without thinking that a customer is left with a useless piece of ultra-expensive speaker (it cost ₹32,000 in India) only after 2yrs of usage!
That's not the case with any other expensive products from brands like Sony, Bose or Marshall. They simply last more than a decade or even multiple decades without any issue.
You guys can at least offer a software-based solution through updates by giving an option to allow touch panels to be disabled by the software. I am sure that's not a rocket-science and this simple fix may bring relief to your HomePod customers across the world who are either facing or are going to face this ghost-touch issue."
All HomePod customers across the world would be grateful to Apple for introducing this software fix.