I don't have a problem with reusing character concepts. I do it all the time. Most often, I reuse bits and pieces and adapt the rest. 

Emmie, for instance, is technically a reuse of a very old character of mine that never got any play. They share a name and face claim ([url=https://www.instagram.com/kacyhill/?hl=en]Bill Murray[/url]). In terms of personality, past, etc., they're (as far as I can remember) totally different. 

I think the metric to look at is "does this character fit the RP and add something valuable to it?" rather than "have I ever used somebody similar before?"