Currently, there is no distinction between "warning" messages and "information" messages (see also https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#diagnosticSeverity): both are highlighted in yellow in QtC.
Other editors highlight information messages in blue, like VS Code for example:
as warning:
as information:

See also Main.qml in attached project: one warning should be yellow while the "unqualified" one should not be yellow (as its marked as info in the .qmllint.ini file).