I have tried: response.flash="Auswählen" (German for "select") and I got "Ausw%C3%A4hlen". Looks like urllib.quote, but why?
And in some other contexts  I got "Auswählen" as expected. I could not find any rule.

I am using the trunk from yesterday.

Then I wrote some test functions. I have written the results after each block:

def flash1():
    redirect (URL('flash1a', args=['hello there']))
   
def flash1a():
    response.flash=request.args[0]
    return dict(text='done')

Result:  hello_there  (with an underscore in place of the space)
------------------------------------------------------

def flash2():
    redirect (URL('flash2a', args=['hello there äöü']))
   
def flash2a():
    response.flash=request.args[0]
    return dict(text='done')

Result: Invalid request. I thought "args" uses urllib.quote?
------------------------------------------------------

def flash3():
    redirect (URL('flash3a', vars=dict(t='hello there äöü')))
   
def flash3a():
    response.flash=request.vars['t']
    return dict(text='done')

Result: hello there äöü  ok!
------------------------------------------------------

import urllib   
   
def flash4():
    response.flash='hello there äöü'
    return dict(text='done')

   
Result:  hello there äöü  ok
------------------------------------------------------

def flash4a():
    response.flash=urllib.quote('hello there äöü')
    return dict(text='done')

       
Result: hello%20there%20%C3%A4%C3%B6%C3%BC  ok
------------------------------------------------------

def flash5():
    redirect (URL('flash5a', args=[urllib.quote('hello there äöü')]))
   
def flash5a():
    response.flash=urllib.unquote(request.args[0])
    return dict(text='done')   

Result: invalid request   
------------------------------------------------------

def flash6():
    return dict(load=LOAD('default', 'flash6a.load'))
   
def flash6a():
    response.flash='hello there äöü'
    return dict()

Result: nothing!!
------------------------------------------------------

def flash7():
    return dict(load=LOAD('default', 'flash7a.load', vars=dict(t='hello there äöü')))
   
def flash7a():
    response.flash=request.vars['t']
    return dict()

Result: nothing!

Some strange results, isn't it?

All functions again if someone wants to try it himself:

def flash1():
    redirect (URL('flash1a', args=['hello there']))
   
def flash1a():
    response.flash=request.args[0]
    return dict(text='done')

def flash2():
    redirect (URL('flash2a', args=['hello there äöü']))
   
def flash2a():
    response.flash=request.args[0]
    return dict(text='done')

def flash3():
    redirect (URL('flash3a', vars=dict(t='hello there äöü')))
   
def flash3a():
    response.flash=request.vars['t']
    return dict(text='done')
   
def flash4():
    response.flash='hello there äöü'
    return dict(text='done')

import urllib   
   
def flash4a():
    response.flash=urllib.quote('hello there äöü')
    return dict(text='done')
       
def flash5():
    redirect (URL('flash5a', args=[urllib.quote('hello there äöü')]))
   
def flash5a():
    response.flash=urllib.unquote(request.args[0])
    return dict(text='done')   
   
def flash6():
    return dict(load=LOAD('default', 'flash6a.load'))
   
def flash6a():
    response.flash='hello there äöü'
    return dict()

def flash7():
    return dict(load=LOAD('default', 'flash7a.load', vars=dict(flash='hello there äöü')))
   
def flash7a():
    response.flash=request.vars.flash
    return dict()

Any answers welcome!
Regards, Martin