That is something for Khaled to decide, IMO.
is for Khaled to decide. That doesn't mean no one should comment on anything. I'm certain Khaled takes into account not just the suggestions, but the general opinions of those who post as well as any good or bad points that are stated regarding a specific feature. There really isn't anything wrong with agreeing or disagreeing with a suggestion and giving reasons why.
Regardless, this suggestion has been suggested so often that I think every pro and con has already been stated many times already.
The "short" answer for the OP - the suggestion is known and has been known to Khaled for a LONG time. It would require redoing how the edit line works to allow for underlining and hotlinking. Khaled would also need to either select a set of dictionaries that he thinks will never go away or else he will have to manage his own set. It doesn't help to use third party items in a program only to have the people who manage them disappear. Most programmers generally avoid that kind of situation whenever possible. Exceptions are of course for major companies (such as using .NET because you know M$ isn't going away). Maybe Khaled can find a dictionary set for most languages that he feels will be reliable and long lasting so he doesn't have to worry about it. That or he has to cater to the ability to let users pick their own dictionaries and that can be a pain as well. And considering scripting works (it may not be perfect, but it does work), I have a feeling the feature is far down on his list of things to do. That being said, I
do believe he has it on his list of things to do. Of course, that's just a guess.
