The discretionary break character is an awesome addition. But I think it came with a bug:

When typesetting text that contains URLs, I use a GREP search to find all URL strings in order to globally apply a character style with Language set to [No Language] in order to suppress any auto-hyphenation.

I then use some search-replaces to globally insert discretionary breaks in places I don't mind URLs breaking, such as preceding periods and hard hyphens. This technique can still leave too-loose or too-tight letter-spacing when URLs contain long unbroken letter strings, and in those cases I insert discretionary line breaks where I want them (often recapitulating hyphenation in actual words contained in URLs, or just wherever if the URL contains a long random character string of some sort).

ANYWAY. Sometimes, unpredictably, if I use Type: Insert Break Character: Discretionary Line Break to insert a discretionary line break, then highlight the character and copy it, and then try to use Paste to insert the discretionary line break character elsewhere, instead of inserting the discretionary line break what happens is the letter immediately following the insertion point gets deleted.