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I noticed that the Delphi RAD XE underlines in red incorrect codes and also I’ve seen the Dephi 7 do the same, this an image describes well what I mean. 
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Everton, this feature has been introduced since Delphi 2007, if I’m not mistaken. I’ve never seen it on Delphi 7, but the name of the feature is Syntax Checker. There are plugins that can help you like Cnpack or Delphi Experts.
Updated on 13/08/2018
As our colleague @aguena mentioned, this feature already exists in Delphi 2006. In the Code Insight options you can enable and disable Error Insight, which is the plugin responsible for highlighting lines the IDE thinks are wrong. But in most cases she highlights lines that are healthy, I particularly ignored them (did not turn off).
I believe that because Delphi is a compiled language, the IDE often waited for a compilation (even in the background) to validate errors or not. So the lines were always highlighted. Until today this behavior occurs, but less often.
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My version of Delphi is the 2006 (Turbo Explorer) and it already offers the Code Insight in the IDE.
Among the resources of Code Insight, the Error Insight is what highlights in red the locations of syntax errors. But this feature has many bugs (even in the latest versions of Delphi) and sometimes indicates bugs that do not exist.
If these indications become bothersome, simply switch off the Error Insight.
In my version, the way to turn this option off is: Tools -> Options -> Editor Options -> Code Insight. Once in this window, just uncheck the option Error Insight.
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