Maybe I'm wrong, but as you copy a text, you should get it as it is was encoded.
In PDFs, copying a text where ligatures are applied as Ot features makes you obtain plain text (no ligatures).
Of course if you hard-code a non-standard glyph into your text, you could have issues when copying it.

Yes.

I would say no ligs.
The reader isn’t just going to read the URL as a word, but may also decide to key it, character by character, into a browser field.
For that eventuality, don’t complicate with a ligature, use discrete characters.

As a general rule I agree with Joe that ligatures should be avoided in email addresses and URLs. I think an exception is possible in the case of domains consisting of single, common words, presuming the text is appropriately spaced (always important when ligatures are involved). So, for example I think you can get away with fiction.org, but not morefiction.org, and definitely not moreoffiction.org.

Thanks guys. I think I'm going to go with taking them out of every address. I understand what you're saying John about maybe getting away with common words in short emails, but then I think we'll get into the realms of um-ing and ah-ing over what is possible.

What has really swayed me in the direction of being militant about no ligs is the fiftymilesofideas.ca web address Joe shared. I think even the jedis felt THAT disturbance!