the worst that could happen is either (1) grid tries to take more power than Teletype is prepared to give, causing Teletype to shut down or (2) grid pushes your power supply harder than it wants to go and your case acts funny or doesn’t work.
Both of these should be fixed by unplugging the grid and power cycling, but since it’s Eurorack I cannot promise that there isn’t some corner case where more serious problems could occur.
by “powering the grid by itself” we mean using some sort of USB power splitter so that the grids data is connected to Teletype, but it’s drawing current from its own outlet.