Hmm, well at Ren's prompting, I tested it out myself. It really does seem like a bug, and an odd one to me. I took screenies with my great foreseeing powers, so I'm posting them with wonderful explanation.
1) 2) 3) 4)
1) my original stats: 94 ap and 30 xpl; you can also see my friends list (in the next two screenshots I delete Lulu, Metal Bunny and phlegmtheorem in order )
2) now I have 74 ap, which is right and fine as deleting friends is supposed to take 20 ap, but I also gained 59 xpl. O_O That's quite a lot... esp. considering I wasn't supposed to gain any at all but lose 5.
3) once again, I lose 20 ap. I expected to gain 50 xpl, but I instead lose 20. The screenshot looks like it cut off the bars in two places; in case it's hard to read, the 54/100 bar is "Action points," and the bar under "Exploring points" is supposed to be 69/30.
4) after Ren mentions losing 20 xpl each time he does it more than once in a row, I try after the counter resets and gain 20 xpl.
Ren's tested a couple of times. He tried 4 times in a row, and after the first one (gained 65 xpl, shown in first screenshot in his post) he kept on losing 20 xpl. I think that this stops once the counter resets, although I only tested it once.
It also seems like the value you gain is random for the first removal. Although for the last two times I gained/loss a multiple of ten, the first time I gained 59, a prime number. Ren says got 67 (or something similar) and 42 once each.
EDIT: fixed some errors X) ty to Ren for pointing out that I gained 59, not 50.. *needs to start wearing glasses again* I also took a look at the screenshots and noticed that the bars in the third one were cut off in some places.