Hi Arix,
From the Edit tab you have on the top while creating or replying on a post, you have an option to insert code. When you click on it and whatever you paste into the box will be copied to the post with a black background.
{master}
labroot@Spine01-re0> show version
Hostname: Spine01-re0
Model: qfx10008
Junos: 17.3R3-S2.2
JUNOS OS Kernel 64-bit [20180911.6c98660_builder_stable_10]
JUNOS OS libs [20180911.6c98660_builder_stable_10]
JUNOS OS runtime [20180911.6c98660_bui
Just an example.
Regards,
Pradeep Kumar.