It looks like the forums thinks that everything after .com is the extention to the file. That's why it is chopping it off.
Allowing people to post a (supposed) image with *.com or *.exe extenstion is a BAD idea. Those are executable files and any Windows computer will try to execute (i.e. run) them as a program instead of displaying a file.
And allowing someone to post a (supposed) image with no extention (like your links) is also a danger since it is possible to redirect that to anything, including an executable program.
For security reasons, all images must have a valid extention like *.gif, *.jpg, etc. Othewise you are opening yourself up to malicious files being uploaded instead of images.