Rephrase comments.

src/threading.c

@@ -408,24 +408,23 @@ jl_ptls_t jl_init_threadtls(int16_t tid)
 
 JL_DLLEXPORT jl_gcframe_t **jl_adopt_thread(void)
 {
-    // jl_init_threadtls puts us in a GC unsafe region, so ensure GC isn't running.
+    // `jl_init_threadtls` puts us in a GC unsafe region, so ensure GC isn't running.
     // we can't use a normal safepoint because we don't have signal handlers yet.
     // we also can't use jl_safepoint_wait_gc because that assumes we're in a task.
     jl_atomic_fetch_add(&jl_gc_disable_counter, 1);
     while (jl_atomic_load_acquire(&jl_gc_running)) {
         jl_cpu_pause();
     }
-    // In `jl_safepoint_start_gc` we observe if a foreign thread has asked to disable the GC
-    // Guaranteeing the order of events.
+    // this check is coupled with the one in `jl_safepoint_wait_gc`, where we observe if a
+    // foreign thread has asked to disable the GC, guaranteeing the order of events.
 
     // initialize this thread (assign tid, create heap, set up root task)
     jl_ptls_t ptls = jl_init_threadtls(-1);
     void *stack_lo, *stack_hi;
     jl_init_stack_limits(0, &stack_lo, &stack_hi);
 
     // warning: this changes `jl_current_task`, so be careful not to call that from this function
-    // `jl_init_root_task` assumes that GC is disabled.
-    jl_task_t *ct = jl_init_root_task(ptls, stack_lo, stack_hi);
+    jl_task_t *ct = jl_init_root_task(ptls, stack_lo, stack_hi); // assumes the GC is disabled
     JL_GC_PROMISE_ROOTED(ct);
     uv_random(NULL, NULL, &ct->rngState, sizeof(ct->rngState), 0, NULL);
     jl_atomic_fetch_add(&jl_gc_disable_counter, -1);