If you're a "production person" or "front end developer" it's not an issue, however if on the other hand you're selling yourself as a "creative professional" it

If you're a "production person" or "front end developer" it's not an issue, however if on the other hand you're selling yourself as a "creative professional" it's a bad idea. The only exception might be if you used a super minimal theme and re-designed it from the ground up so it doesn't look anything like the original.