Is easy to know when a non english speaker is writting?

Welp, self explanatory.

In spaish is easy to catch foreign speaker (even writting), but... is the same for us foreign speakers?

My job has taken me all over the world but every meeting and conference I have ever attended has been held primarily in English. I have so much admiration for those that are operating in a technical field in a non-native language. I can’t really imagine how difficult it must be. I see posting and discussing all things audio here on this forum in the same vain.  My hat is off to all those conversing in a second language. 
The sentence structure gives it away many times.I too admire anyone that can navigate English as a second language.
Nothing worse than an English only speaker criticizing someone whose second or third language is English.
It’s kind of like a Turing test for language....

In terms of detecting that someone is using English as their non-native language, it would also depend on the level of mastery of the “foreign writer” and the educational level of the reader. 
If anyone likes to read, check out Through the Language Glass by Guy Deutscher. He explains how language actually shapes thoughts. An example may be that French contains 7500 different ways to express color. This is an exaggerated number but it proves they can perceive more about something’s beauty because they have a lot more references.  Also German has a lot more direct and absolute terms. While it may seem “harder” it’s beneficial in engineering.  It’s a good read if your into the subject. I thought it was fascinating. His daughter is Alma Deutscher, the violin and piano prodigy.