This may seem like a minor inconvenience bug but I don't know what is actually broken with this bug and whether it extends to further areas.
**Steps to reproduce: **
1. Be logged in (such that pasting formatting into the source editor prompts it to ask you if you want to convert it to wikitext).
2. Find any Wikipedia article with at least 2 categories listed at the bottom.
{F31453488}
3. Select the categories such that the gap between 2 categories is included in the selection.
{F31453490}
4. Find any other page on Wikipedia (not other Wikimedia projects).
5. Edit the page in source mode and paste your selection at the end of a line (including a blank line), not in the middle of words, such as here:
{F31454335}
The following should come up:
{F31453494}
6. It doesn't matter what button you click. Click either.
**Actual results:**
Nothing is pasted, and pasting is now broken. You can copy anything at all and it won't be able to be pasted into that source editor.
You can fix this by switching to visual editor and switching back again.
**Expected results:**
The category text should be pasted either without any spaces or new lines or with spaces or new lines between each category, as it is in other input boxes. Pasting ability should be intact.
**Notes:**
According to Notepad or online Unicode identifiers, there is no character between the "(±)" and the "S" (other than new lines or spaces). But according to Wikimedia projects other than Wikipedia (like Wiktionary or Wikimedia Commons), where it is possible to paste this text and have pasting remain intact, there is an unknown space character between the categories which appears on each new line. Copying and pasting this character anywhere is impossible, as it's not a real character but a glitch. Selecting it with Shift-Arrows also causes the text style to change to blank:
{F31453503}