question on creating links in plain text messages

Question - is this a bug in balsa, or in one of the underlying  
libraries, or is it just an unfortunately side effect of trying to find  
URLs in plain text.

I have received (as an example - it happens at a non-trivial rate) a  
message (plain text only) which includes the following line:

https://bugs.kde.org/show_bug.cgi?id=405506. Could someone familiar  
with craft help me with this one.

Unfortunately, when balsa displays the message, the URL it links to  
includes that trailing period, so in this case leads to an error, as  
"405506." is indeed not a valid bug number.

So - where in the process of displaying plain text, is a URL detected  
and turned into a clickable link?

I somehow think I have brought this up in the past, but can't currently  
find any reference.  I do, however, find lots of posts about this  
issue, with no consistent conclusions.  The most useful suggestions are  
to reword the sentence in the first place, but that's obviously too  
late in my case.  The period is indeed a legitimate character in a URL,  
but not likely included when followed by whitespace.

Any info or other opinions?

Jack