Hi Ruud,
It appears the style is being added to the div surrounding the textbox and that's the reason it's not working. We will have this fixed in the next update. What you can do in the meantime is to put a class on the table cell and add this to your theme.
Like so:
.default .ExampleClass div input {
font-weight: bold;
}
I hope this helps.
Can you try it with css instead of inline styles?