Yeah, I have to stop myself from using HTML at this very forum. <i>It's so annoying!!</i>
That goes for any language, though, not just scripting. There's a name for it (well, actually two names): Proactive interference is when knowledge you already know interferes with what you're trying to learn, and retroactive interference is when knowledge you're trying to learn interferes with what you already know. In high school, I took 1 year of French before I decided I didn't like it, then I had 2 years of Japanese. I would get small words, like "and" confused in both languages ("et" in French and "to" in Japanese). Or pronouns, like "I." Don't know how many times I tried to start a Japanese sentence with "Je..."