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?

Well, in my experience, English is not quite the - common- language shared by many other than American English speakers.

There is the different spelling of numerous words in American English, secondly, in my learning, American English seems to have a preference for a different (more simple?) sentence structure. 
This also goes for the 'preferred' absents of punctuation marks, other than full stops (i.e. periods :) ! 

This is not negative by any means, and can often contribute to a faster apprehension of what has been said. This also by the shorter sentences. 

However! It also lends itself to saying things that can be equivocal, and in my experience perhaps on purpose - when e.g. reading marketing 'spiel' like IT manuals.

I'd happened to translate numerous into German and often had a tough time to decide which way to say it. German is generally a lot less ambiguous.

Badly misspelled English text (forget 'your' instead 'you're' :) , add some truely - of the wall- grammar, is easy to detect - often quite hard to comprehend as to WHAT on earth exactly was meant. 

M. 🇿🇦 

Well, in my experience, English is not quite the - common- language shared by many other than American English speakers.


Same here, actually Spanish is more common. My German, Russian speaking skills are pretty limited, but most East EU and West EU folks speak Spanish, French and English. Spanish will bridge the gap, where English won’t sometimes. My Asian, and Island speaking skills are about the same as my German, but French and Spanish will get you a good meal a place to sleep, and hopefully, a good time.

Funny my grandmother, still spoke a dialect of Irish Gaelic. English wasn’t her first learned language, but she preferred to speak and write in english.

c’est la vie, amego!!!

I enjoy reading posts, in any forum, from people of other cultures or nationalities. I can often spot syntax and grammer oddities, but it makes for even more interesting reading. 

I used to teach English as a second language. English is far more easily spoken than written. 

What gets to me are obvious grammer errors and written illiteracy of native English speakers. I see very little of this on Audiogon, but when reading political posts it becomes obvious that "Coastal Elites" do tend to be more literate, regardless of political preference.
This is very important(NOT).
And what's the point of this post?  is there a concern that if identified as a non-english speaker (as a 1st language) that you will somehow be treated differently in this forum?  That would most certainly be a misplaced concern!