<Snipped quote by Darkmatter>
Oliver would probably publicly advertise himself as a mercenary, but would never admit to being a thief. Eolas may have heard rumors that Oliver has been involved in some shady sneakthievery, but Oliver would never admit to it and there wouldn't be any evidence one could really point to beyond those rumors. A good thief probably wouldn't leave behind much of anything that link them to the crime anyhooooooo.
My main point would be that Eolas would know he's done merc work and isn't so much so of an honourable knight.