This isn't a particularly major issue, but I've had this thing nagging me for a while. When looking at QGIS 3.4's global variables, user_full_name is assigned my given and surname, which includes a diaeresis (¨) somewhere in there. I can't seem to find any way to get QGIS to switch/adapt encoding and display the name correctly. The accented character gets switched to that ubiquitous black rhombus.
I looked for info on this behavior and found moderately similar issues like this and this but it's not exactly the same problem as it's not a geodata encoding issue but rather how QGIS deals with values pulled from the OS.
I have tried unchecking the Override system locale tickbox in Options|General as I prefer to use American English even though my OS is set to Canadian French. No effect to observe.
There's somewhat of a workaround right now which is to fix the name in the Project variable project_author as it is editable (it's filled with the offending global variable by default).
I'm curious to know, though, if someone has encountered this before and if there's a solution in QGIS.