So, it's a little 'trick' how you can post any links on YA. Maybe it's not a unique one, but i hope it helps somebody especially who is fed up with the error 999.
The 'trick':
Option 1: Select a question, make an answer to that without your link (write anything), hit preview, hit submit, so your answer is on YA, after that you can edit your answer and now you can write your link in it (which gives you error 999 whenever you try it), hit submit, surprisingly you don't get any fcukin error 999, your answer successfully submitted with your link in it.
Option 2: You can simply put your link not in the answer field but in the sources field

Yup, option 1 is almost 2x work but perhaps it's worth it.
Cheers,
HB