Wikipedia editors often believe in reincarnation — by this, I mean here the ability to change their username, return to the site, and not have the previous username's reputation stick.
IT DOESN'T WORK!
The only ways you can return to Wikipedia under a new name and edit without fear of being associated with your previous identity are:
- You had essentially no previous reputation. If you barely edited at all under your former username, nobody might have enough information to connect the two. But in this case, why change? The only sensible reasons involve not wanting to edit under your real-life identity or the choice of a really dumb first username you realise you'd rather be shot of. In the second case, just get a user rename.
- If you are able to make a wholly clean break with the past - no grudges, no pet articles, no topics you return to, no similar edits. However, be honest with yourself - isn't the reason you want to come back that there are issues you can't just leave?