it produce different results when referencing by object name and "this" including to reactive ui

Are you referring to adding an event like this?

on:click={listenerObj.myhandleEvent}

Then that has nothing to do with Svelte. If you reference a function like that, this will not be bound; that is just how JS works. Which is why you are supposed to use an anonymous function if you want this to be bound to the object the function is defined on:

on:click={() => listenerObj.myhandleEvent()}

I do not see any wrong behavior here.

There is something off about how the event handler object is attached, though...

If the handleEvent method only contains the log statement it is attached via:

listen(button1, "click", /*listenerObjHandleEvent*/ ctx[1])

If an increment statement is added (listenerObjHandleEvent.count++), that code changes to:

listen(button1, "click", function () {
    if (is_function(/*listenerObjHandleEvent*/ ctx[1]))
        /*listenerObjHandleEvent*/ ctx[1].apply(this, arguments);
})

And since the handler object is not a function, it will no longer work.

Thank you for quick reply, yes I saw compiled code in REPL

listen(button1, "click", function () {
    if (is_function(/*listenerObjHandleEvent*/ ctx[1]))
        /*listenerObjHandleEvent*/ ctx[1].apply(this, arguments);
})

My Intension is to want svelte compiler support listener object with a handleEvent() according to the DOM API specification.

Closing per discussion on #15856