If you were able create a widespread campaign where the vast majority of traders and HODLers could hold their Bitcoin for 30 days, what would be the effect? Would the dramatically reduced trade-able supply boost the price or would low liquidity ultimately hurt the price?
Firstly, how would you be able to create this "campaign"? It's simply unfeasible and impossible to make it work because of the sheer number of people that you have to convince. Add the fact that bitcoin is decentralised, you will never make this work in practice.
Secondly, even if it did work theoretically everyone would know that bitcoin's supply has been artificially suppressed, and as a result I expect investors to back out of purchasing altogether, leading to reduced liquidity. Another possible scenario would be that people would speculate and gamble, but that would only be something short term which will eventually collapse.
Either way, I don't think that this type of centralised manipulation would ever work, and if it did, it would in fact significantly hurt bitcoin in the long run especially with the public's perception of bitcoin being changed to something that can be easily manipulated.