Mail changes attachment filename

Question

Mail.app has a bug or disability to properly interpret the filename of received attachments if the filename contains accented characters.
for example
the original filename:  xxxxx xxxxxx xxxxáxxxxüxxxxx_xxxxxxxx xxáxáx.pptx
when received in email: k=5Fxxxxxxxxx_xx=E1z=E1k.pptx?=
it does not matter what email client is used to send the attachment, it can be any version of Outlook or OS X's Mail, the problem is with Mail.app on recipient side.
Also it happens to users of 10.6.8 trough to 10.9.1
What is strange, that this behavior of changing filenames is not consequent:
in the past before I realized it's a bug, I was usually asking the sender to resend the email as I thought the mail was damaged.
The sender did nothing else, but resending the email from her/his 'Sent Items' folder, so no change has been made to filename
or content of the email itself > and strangely the second time the attachment is displayed correctly with proper accented characters,
no extra letters at the beginning or after the extension.
I also tried to reproduce this bug, sometimes successfully, but as I wrote this bug is not consistent.
What worries me that apple knows about this bug for years, but does nothing to fix it - it still exists,
and non-English users suffer from this.
https://discussions.apple.com/message/6808962#6808962
https://discussions.apple.com/thread/1409364?start=60&tstart=0
https://discussions.apple.com/message/7195409#7195409
Of course I filled a BUG report, and the purpose of this post is to ask other OS X users to fill a BUG report too and make some pressure
on apple to fix it for once and for all.
for non developers a link to bug report: http://www.apple.com/feedback/macosx.html
for developers:     https://bugreport.apple.com/
A kindly ask the moderator not to close this Discussion until apple delivers a permanent fix.
Asking the sender not to use accented characters in filenames is not a solution it's a workaround that nobody will use,
as it puts everyone in an inconvenient position when exchanging files with clients.
Thank you.

Answer 1

Also have this frequently.
What's more maddening, files within the same message, with the only accented character being the same in each file, and many other files with (different) accented characters, one file gets corrupted, the other one doesn't.
As in Mail.app:
The same message appears fine in iOS.