Is it permissible for RHO to announce to LHO "no questions partner" before LHO has selected his/her opening lead?
Difficult to see what it could suggest.
On the one occasion that I did call the TD for this (frequent) deviation, he asked me "and how have you been damaged?" My response that I had been irritated by it and this had distracted me from my usual immaculate, accurate bidding and play was wasted.
There's nothing we can do, is there? We will not be able to stop them doing it and there seems no punishment.
Yes - but almost always it is an honest (albeit misguided) effort to speed up the process. Judge Jeffries (or The Secretary Bird) might impose a DP under Law 74, but unless any indication of attempting to provide UI is suggested by the other side, I would consider doing nothing more, if called, than saying "Well technically they are right - but I don't think it really matters that much in this specific instance".
I think a warning is in order, since it's a violation of procedure and could give UI. How many times you give a warning before switching up to a PP or DP is probably down to how grumpy you're feeling.
I assume that saying "No questions" is a remark in 74A2
Again "carefully' is imposing a very high standard of care.
The 'Any questions?' comment is to protect partner's rights under 41B. I hope no one is considering that this is being asked "solely for partner's benefit" under 20G1 - although I suspect that technically it might. One to consider.
I always aim the "any questions" at the table as a whole, not just my partner. For example, if dummy or declarer has given MI (e.g. a missed alert, which is often impossible to guess unless you're told), they should be correcting it while my lead is still face down, as there's still time to fix things in that situation. So I need their permission to continue before facing the lead. (Because of this, I normally phrase it as "any questions or clarifications?")
In practice, people often forget this, so I pretty much have to yell at the opponents to not face the lead if I happen to be on the declaring side in that situation.
What I do is to keep my lead face down and wait for the declarer to signal that I can face it. No need for anyone to say anything.