I feared the S piece until it saved my solve
I kept postponing the S piece. The grid asked for something crooked, and I kept forcing an L.
The solve started well. Long regions took the I, cornered ones took the L. I shaded four cells per region and kept the shaded mass connected. No 2x2 squares. Same letters stayed apart so they would not touch even at corners. Midway, two regions in a row both wanted something bent.
The region that fit nothing
I placed a T in the first one. It broke connectivity: its tail hit an empty region with nowhere to continue. Erased. Tried L. Now two L shapes stared at each other across the border, nearly touching at corners. Erased that too. I sat there thinking the grid was broken. The "Hint" button shaded one cell in a way that spelled S. I snorted and built it out anyway.
The S sat sideways and ugly. And suddenly everything clicked: its upper step reached the mass above, its lower step ran toward the next region. The connectivity I had worried about fixed itself. I closed the second region with an S without hesitating.
My crooked letter
Now when my hand reaches for the familiar L, I try the S first. Most of the time the grid wants exactly that.