dlang feed, thunderbird

[number]

I don't get any posts for this forum in Thunderbird since today. 
It worked previously.

the URL : https://forum.dlang.org/feed/posts
works in Firefox, but creating a new account and subscription in 
Thunderbird he says 'The Feed URL is not a valid feed' and the 
validation link gets me here:
http://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fforum.dlang.org%2Ffeed%2Fposts

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This feed does not validate.

     line 868, column 136: XML parsing error: <unknown>:868:136: 
reference to invalid character number [help]

         ... an>On 2018-05-22 18:34:34 +0000, Ali &#x03;‡ehreli 
said:
                                                      ^

In addition, interoperability with the widest range of feed 
readers could be improved by implementing the following 
recommendation.

     line 171, column 87: Two entries with the same id: 
https://issues.dlang.org/show_bug.cgi?id=18898 [help]

         ... 
//issues.dlang.org/show_bug.cgi?id=18898</id><title>[Issues] 
[Issue 1889 ...
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Ali, your book is awesome, but now you broke the feed! :)

any ideas?