Magick used for vengeance is only wrong when you know there is a much easier, much more practical, much less harmful way of handling it. For instance if someone stepped on your toe, do not curse them with penguin feet, simply ask them to watch where they're going.
Always remember, magick isn't for everything. Practical situation cause for practical solutions.
Yes, it very possible to effect someone with magick when not deliberately intended upon that specific person.
Just my opinion on the real name/face thing: this isn't DeathNote, lol. You can pick up on someone's energy if you know something they like very much. If it is someone you only know online, then you can connect via the avatar they commonly use, a manner of typing unique to them, etc. I'd say not knowing the name/face can make things a bit more difficult, but not that much so if you are used to sensing energy. The computer is a wonderful medium, putting people just a screen apart, so to speak.
I have heard of people writing spells into regular text, via specifically placed typos, capital letters, or other oddities. And when the writing is read it casts the spell. It sounds kinda like crazy, complicated stuff, but a letter or word can also act as a sigil of sort that when looked at or considered it is "fired off".
Too much for my little brain to try and do. I just let bygones be bygones.
The mistake of doing a Revenge Spell is that you have given up making decisions on how you can work things out for the good without magic... Only the weaklings are the ones who do it, the Cowards...
It is also a mistake if you have not literally exerted any effort in learning from your mistake before doing what you have done...
It is not because you would feel relieve that is why you did it, it is not because it has helped you even a bit, it is because you did not try to solve it and made the decision to try taking Revenge with the use of Magic... That is the Mistake....
Connecting with others through the computer is a great thing, but it is things like this that scare some people. Because of my worry I give this advice.
Protection magic is the first type of magic one should learn. It can be very basic but it can become very complex over time. Shielding is a skill associated with protection. Learn to build shields through meditation. Open up your third eye and use it so that you will be less likely to follow a ''wrong'' path (for you). ;)