updated comment in main.cpp

src/main.cpp

@@ -225,6 +225,9 @@ FIXME: The new optimized map sending doesn't sometimes send enough blocks
 
 TODO: Map saving should be done by EmergeThread
 
+SUGG: Map unloading based on sector reference is not very good, it keeps
+	unnecessary stuff in memory. I guess. Investigate this.
+
 Environment:
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