Clarify comments about KT-36625 that it is pending design decision.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmStringConcatenationLowering.kt

@@ -114,10 +114,10 @@ private class JvmStringConcatenationLowering(val context: JvmBackendContext) : F
     override fun visitStringConcatenation(expression: IrStringConcatenation): IrExpression {
         expression.transformChildrenVoid(this)
         return context.createJvmIrBuilder(currentScope!!.scope.scopeOwnerSymbol, expression.startOffset, expression.endOffset).run {
-            // When `String.plus(Any?)` is invoked with receiver of platform type String or String with enhanced nullability, this SHOULD
-            // fail a nullability check (NullPointerException) on the receiver. However, the non-IR backend has a bug (KT-36625) where this
-            // check is not inserted (see KT-36625). To maintain bug compatibility with the non-IR backend, we remove IMPLICIT_NOTNULL casts
-            // (which generate the nullability checks in JvmArgumentNullabilityAssertionsLowering) from all arguments.
+            // When `String.plus(Any?)` is invoked with receiver of platform type String or String with enhanced nullability, this could
+            // fail a nullability check (NullPointerException) on the receiver. However, the non-IR backend currently does NOT insert this
+            // check (see KT-36625, pending language design decision). To maintain compatibility with the non-IR backend, we remove
+            // IMPLICIT_NOTNULL casts from all arguments (nullability checks are generated in JvmArgumentNullabilityAssertionsLowering).
 
             fun IrExpression.unwrapImplicitNotNull() =
                 if (this is IrTypeOperatorCall && operator == IrTypeOperator.IMPLICIT_NOTNULL)

compiler/testData/codegen/box/strings/stringFromJavaPlus.kt

@@ -36,13 +36,14 @@ public class J {
     }
 }
 
-// FILE: main.kt
+// FILE: stringFromJavaPlus.kt
 import kotlin.test.assertEquals
 
 fun box(): String {
     val n = 123
 
-    // Due to KT-36625, certain concatenation calls below (marked with a comment) SHOULD fail a nullability check but do not.
+    // Null check behavior in string concatenation might change depending on language design decision for KT-36625.
+    // Cases below that could be affected by KT-36625 are marked with a comment.
 
     assertEquals("null", "${J.platformStringIsNull()}")
     assertEquals("nullBAR", J.platformStringIsNull() + "BAR")  // KT-36625