The wysiwyg editor takes text formatting from the source when copy/ pasting. So if you copy your link from a link in a web page as opposed to the unformatted text in a browser address bar, it will paste the formatting information too (or a close approximation of it.)
It's irritating at times, yes, but if you use the quick reply instead (which I use 99% of the time, it's at the bottom of every thread) there are no formatting options, so you won't encounter these issues ever.
The editor you're having trouble with is the standard one for the forum software. We haven't altered it in any way.
The 500 error is a surprise though - I thought I'd hunted that one down and hung it on the hotel wall.
Might I also humbly suggest that you try posting while sober and see if that helps at all?..