I mistook you with garden2. Accept my apologies.
"For example, Icelandic is typically considered the most difficult language for non-natives to learn."
Perhaps among English speakers (obviously, I don't know), but I usually found Arabic, Chinese or Japanese considered most difficult languages for non-natives.
I found this article about this matter, in which Hungarian is the most difficult.http://www.usingenglish.com/articles/hardest-language.php
The Basque has some difficulties to Indoeuropean speakers:
different order of the words in sentence (SOV)
flexion of grammatical cases
very complex verbal system
very complex system of prefixes and suffixes
"your responses sometimes come across as bruque"
Perhaps it is because my English is only basic and I aply the language and behaviour politeness rules from my language/culture plus I'm a direct person. Probably a text completely acceptable to me can be rude to English readers.
Sorry about that.