Should I use a personal github account or a new one to publish academic code?
You should use your real name.

My lab has a private GitHub group for internal stuff, as well as a few open public-facing projects. 

Everyone in our group uses their real names or some transparent abbreviation (like jsmith) or one that matches their university email/login ID.

I feel it should be immediately obvious who each person is. It would be mildly annoying if I had to remember who allo was every time, when everyone else has easy-to-read IDs. 

If I was your mentor, I would probably ask you to change it. 

It's fine if you do non-job-related development on that same GitHub account, for the reasons you mentioned.