So, Eastercon is approaching: this year, it’s at the Radisson in Heathrow, the same place where I attended my first convention in 2008 (also an Eastercon)–and my first real experience at socialising in English on a massive scale (I went to Bootcamp and WOTF before that, but I’d never actually dealt with so many people in such a small amount of space).
My first Eastercon will always remain etched in memory as the moment I realised that being fluent was one thing, but being a non-native speaker came with a few annoying side-effects. Here are a few:

• Unintentional idiomatic language:
  English is full of idioms–and it’s made worse by the fact that I have to reckon against a lot of local variations (the ones I know most are UK and US, but I bet I miss out on a lot of others, too, like Indian English and Australian English). Now, I generally know what a given idiom means; but the reverse–knowing that I’m using an idiom when I’m writing–is a lot less obvious. For instance, in Harbinger of the Storm, I have references to “bean counters” that are precisely that: dried beans used as die and counters for the patolli game. However, of course, the word has the other, far more common meaning of “accountants”, providing for much unintentional fun…
• The cocktail party effect (or lack thereof):
  You might not know what the cocktail party effect is. It’s a little magic trick of the brain: when you’re talking to someone in a noisy environment, your brain will automatically edit out the background noise (even and especially if said noise includes intelligible conversations), allowing you to focus on the person(s) you’re speaking with. It’s invaluable in parties (hence the name), but also in restaurants, bars, and other kinds of social functions.
  Sadly, I’m completely immune to it in both English and in Spanish, the languages I speak as a non-native. I think it comes from those hours of classes that forced me to listen to the language in order to understand it (and to fill in little summaries to make sure I’d made out the meaning of the words correctly). Now, when I hear people speak, I have to make a pass at understanding it. Even if it’s a conversation that’s completely unrelated to me. As a result, pub-time with me? I might look a little bewildered if the pub is particularly noisy. It’s not because I don’t care what people I’m saying–but rather because I’m trying to disentangle the current conversation from the four others happening at the neighbouring tables.
• Spelling issues:
  Ah yes. I think part of that one comes from the fact that I’m a visual person, and part of it from the fact that I’m a latecomer to English (I only started investing heavily in it at 16 or so). The most obvious effect of that one is that I will need a long moment to process when you’ve spelled a word. At, say, signings, it’s a little more problematic than I anticipated. I live in terror of the day I won’t have understood someone’s spelling out of their name, and will inscribe a book to the entirely wrong person.
  The other side effect is related to the other way around: if you’re pronouncing a familiar word in a way that I don’t expect, I’ll blank it out as “this funny word I can’t figure out”, even though I quite possibly know that word already. This happens a lot with French words or with words I’ve only seen in writing. I don’t seem to have quite the same flexibility for pronunciation as I have in French: figuring out alternative spellings for words I don’t recognise right off the bat has never worked out for me.
• Accents:
  That one often puzzles my BF. I can understand a lot of the more common accents (Scottish, Irish, Australian, etc.), because I sat for my Cambrigde Certificate of Proficiency back when I was 17, and that part of the training for that included listening to a text which would necessarily be in an accent of the Commonwealth. However, somewhere along the line to fluency, I lost the ability to understand the accents of non-native speakers: someone speaking English with a heavy French accent is going to be very painful for me. I remember we went to a panel at the 2005 Worldcon, which had four native English speakers plus a Japanese man. I couldn’t make head nor tail of what the Japanese guy was saying; my BF, however, couldn’t understand the natives, but could deal with the Japanese accent just fine. I think that for him, all non-native accents are somehow kindred, no matter how different they might be from French. For me, they’re just… too unusual to be parsed, I guess.
  (it’s not that bad, though. A few hours are usually enough for me to pick up a new accent and add it to my repertoire. I had a lot of trouble understanding Jetse de Vries‘ Dutch accent when we first met, but by now it’s become second nature).

So… is it just me? Do you share some of those, or know people who have the same issues? Are there other pitfalls when you’re a non-native?