This allows triggering the connected mechanism without paying.

Not sure what you mean by "activate"...
It's not generating money, if that was the concern.

I'm pretty much sure it doesn't activate it - the pulse of repeater just goes through the depositor. This is what they can fix tho.

Depositor does generate a redstone signal when given required coins, right? Well, it also does pass a redstone signal through itself, so the output can be activated by another signal, hence without paying anything.

@VladisCrafter
It is highly unlikely this could ever be a problem. For as be on a server, the server has very likely a claim/chunk protection, where (other)players will not be able to trigger a redstone signal in any other way.
If this is on a unprotected server, then there is also a chance players just mine trough the blocks instead of paying.

In other words: If players can bypass the pay gate they can also just mine the block.
Can't see the issue here.

You are not wrong, but this still looks like unintended behavior and could also happen by accident in tight spaces.

So if it can be fixed, it should be fixed.

As far as i know that is normal vanilla behaviour. It is up to the player to build correctly.
There are blocks in vanilla that doesn't let redstone signals trough, i think glass.

...and the depositor blocks can also behave like that! That's probably the solution to this exact problem. Right, @winnetrie83?

Yes ofcourse i believe so, BUT.....
It might interfere with the redstone functionality. Just like any other redstone block like pistons and droppers etc etc. They all let redstone signals trough.
So maybe the developers can fix this, but there is a chance it just can't be fixed, because of the vanilla code.