On the pockets degree
Nothing prevents wallets from implementing affordable security measures to guard their customers from undesirable habits.
Bitcoin Core for instance has a characteristic to (by default) reject the creation of transactions with a really excessive payment worth. There isn’t a particular rule to stop charges larger than the quantity transferred, however there definitely may very well be. Different pockets software program could have related and/or completely different preventative measures.
On the coverage degree
Coverage guidelines exist to guard the community, not the person node operator. A rule to stop too excessive charges does not belong right here, because it does not damage the community.
Moreover, it’s onerous to think about what such a rule would appear to be, as a result of the quantity paid/transferred is by design not seen within the transaction (most transactions have change that’s despatched again to the sender, however which is indistinguishable from the “fee” output to outsiders).
The mud relay rule is meant to disincentivize the creation of transaction outputs which might be costlier to spend than their worth. Such outputs are more likely to stay unspent within the UTXO set ceaselessly, slowly accumulating and finally growing node operation prices.
On the consensus rule degree
The identical issues apply right here as for coverage guidelines, besides they should be agreed upon by the whole ecosystem, and are such a lot more durable to alter.
Thus far, this has meant no guidelines in any respect that relate to charges (other than requiring them to be non-negative). That is partly attributable to the truth that what’s “affordable” economical habits could change over time, at timescales a lot shorter than these over which consensus guidelines might be tailored.
