[Wayland] Shift key in textarea = text lost in submission

Seen with QtTestBrowser and Otter browser:

When an uppercase or other shift-key typed character is entered into a textarea, an invisible character gets inserted before it. This invisible character can be tested for by observing the behaviour of arrow keys over it, and it lets itself delete with backspace/delete as usual.

Unfortunately, most web services are rather unforgiving� in face of invisible characters: On Wikipedia, your submitted text will become the empty string, and you will be accused of so called section blanking. On Github's issue tracker, your text will be recoverable, but will either be wholly invisible, or the invisible characters will appear as the unicode replacement character �.

Minimalistic testcase (live version at http:// nerdvar.com/nyttig/http.php):
<p><?php echo $_POST['txt']; ?></p>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<textarea name="txt"></textarea>
<input type="submit" value="Send">
</form>

Further info:
Pasting text written in kwrite does not result in� invisible characters, except that the Ctrl key itself �inserts one. I have yet to try the AltGr key (need to find out how to set/customize the layout).

This does not happen in input type="text" fields, only textarea.