Using Firefox (62.0.3) at least, on macOS I can't enter special characters in Writer, they just don't appear, not even as blank character. Affected are at least € @ [] I can copy & paste them just fine, just adding them directly doesn't seem to work. Tested with online 6.0.4 and 6.1.1
Thanks for the bug report, Florian. I can confirm the characters requiring the Option (⌥) key can't be input. I assume you were using German layout, hence the following all require this key: - €: ⌥-E - [: ⌥-5 - ]: ⌥-6 - @: ⌥-L With English layout, the Euro symbol is an example: - €: ⌥-Shift-2
Tor Lillqvist committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/online/commit/?id=1e97cfc2d2a8ee3e296ddfb7a331466bede4a575 tdf#120438: Don't handle a lone "alt" modifier in any special way
With the fix, this can now be closed. Thanks, Tor!