Comments should start capitalized and end in a period

src/librustc_mir/interpret/intern.rs

@@ -187,15 +187,15 @@ impl<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx
         if let ty::Ref(_, referenced_ty, mutability) = ty.kind {
             let value = self.ecx.read_immediate(mplace.into())?;
             let mplace = self.ecx.ref_to_mplace(value)?;
-            // Handle trait object vtables
+            // Handle trait object vtables.
             if let ty::Dynamic(..) =
                 self.ecx.tcx.struct_tail_erasing_lifetimes(referenced_ty, self.ecx.param_env).kind
             {
                 // Validation has already errored on an invalid vtable pointer so we can safely not
-                // do anything if this is not a real pointer
+                // do anything if this is not a real pointer.
                 if let Scalar::Ptr(vtable) = mplace.meta.unwrap() {
-                    // explitly choose `Immutable` here, since vtables are immutable, even
-                    // if the reference of the fat pointer is mutable
+                    // Explitly choose `Immutable` here, since vtables are immutable, even
+                    // if the reference of the fat pointer is mutable.
                     self.intern_shallow(vtable.alloc_id, Mutability::Not, None)?;
                 } else {
                     self.ecx().tcx.sess.delay_span_bug(