Point is we don’t want contentless post to litter trending even if the intent of those posts are good for the economy

That seems like exactly the sort of tradeoff that should be left to the voters. It is a clear judgment call whether good for the economy outweighs good for trending or vice versa.

Burnpost is a philanthropy

No it isn't. If you burn your own coins, that is philanthropy. If you vote to burn (i.e. not distribute) funds from the reward pool, that is a vote on how to best use the reward pool.

Voters should be free to be voters (i.e. express an opinion by voting without incurring an added personal cost to vote one way or another). There is no other way to fairly measure the value of burning vs the benefits of content on trending (given current UI) other than letting voters take that balance into account.

Not being able to downvote without a personal cost was the situation prior to EIP and it had catastrophic consequences.

When I suggest that voters consider voting later, that doesn't mean voters should be required to do this, or harassed if they don't.