Assuming this name is spelled correctly (which seems likely), and assuming you or the user didn’t mangle the log output in a text editor, and assuming that the users´ home directory is actually C:\Users\Aurélien\ on disk, then comparing with the original log output you presented in the top post:
[0.003 info adapters/standalone.cpp:140 main] User directory: C:/Users/Aurélien/Passeport Elise/Rack2
[0.003 info src/settings.cpp:488 load] Loading settings C:/Users/Aurélien/Passeport Elise/Rack2/settings.json
it seems clear that something in Rack is choking on that special char in the name. >> é << got mangled into >> é <<. It could be something innocent in the log printout function of course, but given the issue at hand, probably not, and likely a sign that Rack is probably still not correct throughout with respect to character encoding and handling.
Line 140 of adapters/standalone.cpp in the Rack code is:
INFO("User directory: %s", asset::userDir.c_str());
As others have pointed out above, crossplatform string and filename handling, especially because of Windows, is a bleeping nightmare.