TYPO3 Core

I want to create a new admin-user with a dot in it (like bernd.wilke). The creation seems to work, but a following BE_login failed.
After creating another adminuser (admin) I was able to login into the BE and there I found an admin-user berndwilke (without the dot).
Umlauts, which are usual in names, are removed also.

At least there should be a BIG warning if characters are removed at creation like:
<span style:"color:red; font-size:150%">username changed from ... to ...</span>

better: remove only a few characters, which can confuse databases: '"<>,;:?*%

searching for the modification leads me to class.tx_install.php line 3732 (case 'adminUser':), where a ereg_replace() removes all but [:al num:]_-

(issue imported from #M3242)