Assessing any penalty can be unreasonable in some circumstances and appropriate in others. I’ll give a couple of examples at opposite extremes.
If it is a touch sensitive clock then hitting the button with a captured piece (a common practice) would not actually start the opponent’s clock. It is easily understandable that a player who saw an opponent hit a clock with a piece may not look to see which clock is actually running, particularly in a time pressure situation. If a player used a piece to hit the clock knowing that it would not actually stop the clock, and did so intending to make a claim when the fooled opponent moved, then a TD might actually assess a penalty on the player that left the clock running.
A player makes the second half of the 50th move since the last capture/pawn move but, while preparing to claim the draw prior to hitting the clock and while still on move, the opponent makes a move that would negate the claim and then says that the claim is thus invalid. In this particular case the opponent has violated the rules and a TD can assess a penalty. The minimum penalty should be allowing the claim. The maximum penalty might be ejection from the tournament (if there has been a pattern of such behavior) since capital punishment seems a trifle harsh.
By the way, example 2 is one reason why a player should hesitate to simply hit the opponent’s clock to start the player’s own time.
At one speed chess tournament using touch move (a side event with hundreds of players at a national event) some players played e4, did NOT hit their clock, and then claimed a win after the opponent responded “on the player’s time”. Some less experienced TDs actually upheld some claims before being informed that such claims were not valid.
I think we’re in agreement here as regards the 50-move draw. Although not specifically stated in 14F, the claimant should stop BOTH clocks after making the claim. Once a claim is made, the opponent may not touch the clock to start his or the claimant’s clock while the TD is being summoned. You said that “a player should hesitate to simply hit the opponent’s clock to start the player’s own time”, and this is why I wanted to point this out - not sure if we DO agree. The idea of stopping BOTH clocks is presented in 14C Repetition of Position, but is not covered in 14F. Wonder if this is intentional?
Oversight–my bad. The player should stop the clock whenever he makes any claim. More problems are caused by not taking this simple step than when the clock is left running.