Is this a known issue?
In Lazarus 1.8.4 FPC 3.0.4 on Ubuntu 18.04 LTS with xfce desktop and using a Swedish keyboard. Ubuntu is running in a VMWare PRO12 virtual machine:

In the code window I cannot enter regular pascal comments delimited by { and }.
But in the Text Editor application there is no such problem. Also elsewhere in Lazarus I can enter these characters just fine, for example in property setting edit boxes.

The { key is entered using AltGr + 7 and } using AltGr + 0.

I have looked in the Tools/Editor/Display/Key Mappings dialog and used its "Find key combination" function to see if these key combinations are reserved, but not...

Turns out that ALL such escaped chars do not work, sometimes the code editor jumps to a different tab or otherwise relocates focus and sometimes nothing at all happens....
I googled and finally found an old forum entry where it was stated that Ubuntu was to blame and that one could try the Keyboard setting in the desktop.

I changed keyboard layout settings from "use system defaults" to Swedish layout and set the keyboard to "Generic 105-key PC (intl.)"

Then the code editor also started to recognize the escaped characters correctly.

The strange thing is that all other applications I have tested (terminal, Text Editor etc) worked fine even before I changed the settings, and inside Lazarus all other places than Code Editor also worked OK.
So there is something special about Code Editor, it seems like.

Anyway I seem to be able to type @{[]}\~ now, did not work before.