"All right," Q can accept that, as well as the tacit information, "but I still think it would be best to have someone other than me look at them. Under the circumstances."
Q hunches, his mouth dry. "I have awful nightmares," he says quietly. "Mostly about him. Sometimes I just hear him laughing." He's gone pale. "I haven't really slept well in years."*
"Well," Q tries to smile, "I suppose I can always obliviate you when we're done."
YAY!!!
*Not to mention how hard it must be to sleep with someones face on the back of your head! Poor Q. :(
He has to do this, both for his own peace of mind and for the animagus transformation. It's either Sirius or Severus and I think he feels more comfortable, or less uncomfortable with Sirius looking inside his head than Sev.