How do I correct someone's work properly?
First things first: I colour mistakes red and use the 'Strikethrough' option. Things I add are green. That covers spelling and grammar pretty well.
But what do you do if the words are correct but not in the correct order? Do you use a third colour? I think using the marker instead of changing the colour of the words themselves might work. Is there a better option?

There are also cases of "unnatural use" where one's spelling, grammar and word order are correct but no native speaker would ever use that expression or that combination of words. Another colour? It gets messy real fast. Especially because I like to leave some annotations of why something is wrong or some examples, maybe even some alternative options to express something in yet another colour.
When I took a first look at the page, I randomly browsed through profiles, questions and notebook entries. I am pretty sure I saw a correction that used footnotes that only showed up if you mouseovered them. How do I do this?

Question

How do I correct someone's work properly?
First things first: I colour mistakes red and use the 'Strikethrough' option. Things I add are green. That covers spelling and grammar pretty well.
But what do you do if the words are correct but not in the correct order? Do you use a third colour? I think using the marker instead of changing the colour of the words themselves might work. Is there a better option?

There are also cases of "unnatural use" where one's spelling, grammar and word order are correct but no native speaker would ever use that expression or that combination of words. Another colour? It gets messy real fast. Especially because I like to leave some annotations of why something is wrong or some examples, maybe even some alternative options to express something in yet another colour.
When I took a first look at the page, I randomly browsed through profiles, questions and notebook entries. I am pretty sure I saw a correction that used footnotes that only showed up if you mouseovered them. How do I do this?

Answer

My biggest problem however is the character limit. I usually have to post my correction in two parts because apparently someone thought it would be a good idea to cap characters. What is this? Twitter?

In some cases what someone wrote does make sense and is technically correct but I have the strong suspicion that what they wrote doesn't mean what they think it does. Do you try to clarify things or would this go beyond the scope of things?

Please take a look at the corrections I have done and tell me what you think.

Ne manquez pas cette occasion d'apprendre une langue depuis chez vous. Découvrez notre sélection de professeurs de langues expérimentés et inscrivez-vous dès maintenant à votre premier cours !