Speaking another language on the FeralHeart forums is not "sternly corrected".
For the example you have given, fellow Kerriki politely implied everything and I personally would not have worded it any other way. Kerriki even gave suggestions to the user so I therefore do not perceive the post to have been aggressive nor "stern" like you are pointing said finger.
While we are apologetic to those who deem our response to foreign languages rude and aggressive, we have been going by this rule in a respectful manner for a long time. How it is read is not something we can control and unfortunately this is why users are having misunderstandings with us in the first place. People misunderstand the choice of wording, then spread word of how aggressive/rude/terrible we apparently are for enforcing a rule. Same applies to a lot of things we've done over the years.
It is treated differently on the forums because I have already mentioned, the use of communication when we seek help on the forums.
If we cannot answer a question because it is in another language, Google Translate is an awful and untrustworthy source, how else are we going to resolve the communication issue by asking for English to being the language they use (if possible) before we can resolve the problem they may be having in the game? Truth is, we can't.
Staff cannot speak every language known to man and we have to work with this.
I can and will say that the Staff are only advising because that is what we are doing and we will do nothing more, nothing less.
In the eyes of the community this apparently, in some cases, is not good enough. Which is where things seem to kick off and people get worked up and make us out to be terrible people for having such a rule.
Being a "slap in the face" is a prime example of people thinking of the worst case scenario(s).
Threads can be up for years and may not be used until many more years down the line. Just because this suggestion has been brought up, it does not mean it will most definitely be used. There are things Raz considers more important to be done and - like General chat - there are some ideas we like - like this one - but would much rather come to a conclusion more a little later one when what is more important to him, is done first.
Just because we haven't told you what you'd like to hear now doesn't mean we won't do it later in terms of conclusions/whether or not we'll use it in some form.