I don't think anyone starting out is scarring their reputation. Being new and an asshole will scar your reputation, but being new, humble and learning won't. You see if all the time on Stackoverflow and even here. If you ask a question and need some help, if you are humble and accept feedback to learn you are rarely every criticized. But if you are a douche you'll be called out quickly and rightfully.

I agree that the memory is basically never ending now, but you also have to realize most people will generally only judge you on your recent abilities, not something that transpired years ago, unless it is just so egregious that it can't be ignored. And everyone had to start somewhere, which I think almost everyone gets.

Lastly, don't let fear cripple you into not doing jumping in. Do it, and when you are wrong, just admit it and move on. The tech community while sometimes judgmental and even cruel in their comments is also probably the one place that really does value contributions over mistakes. And at least in my opinion if your contributions and attitude outweigh the mistakes people are really accepting.