:sl: I agree with Al-Mufarridun's post too.
For example, the way some members on this board type their responses in what seems like 40% English and 60% badly transliterated Arabic is incredibly off putting to the many people who may not have heard those Arabic words all their lives. When speaking English with people who aren't at your level, it just seems unnecessary to use Arabic words when English words would suffice... Those who are doing the speaking don't really ever realize how alienating it can be, and I've definitely seen how it discourages both Muslims and Non Muslims from engaging with other more knowledgeable Muslims or Islamic Organizations.
I used to feel somewhat alienated when I first came on this forum due to the above reason. However, the more I hung around, the more I learnt and eventually I've grown to use some of these words which I was first unfamiliar with myself.
At the end of the day though, it is an Islamic forum and therefore I don't feel it's unreasonable in the slightest that such jargon is used. If we go to any other niche forum (e.g. physics, gaming, motoring), we'll notice exactly the same behaviour - i.e. genre specific terminology will be used. There's nothing wrong with that and it's up to the individual to grow and come to terms with it, rather than have people who have used these words all there lives without a second thought having to double check every word they write.
Using Arabic/Islamic terms without explaining the meaning to non-muslims is obviously going to be impolite and unreasonable but I don't believe there is any reason to withold when talking to fellow Muslims (granted, we don't have control over who is reading our conversations). Of course, it would be a good idea to translate when we are unsure whether the person we are conversing with understands or not.
We can't expect to look after the tiniest needs of everyone who sulks and moans cos they don't understand something and in any case, with the wealth of the internet around, anything that is unfamiliar can be learn't in a matter of seconds. Newcomers might find it difficult initially but if they are sincere, inshaAllah they will stick around and, importantly, Allah will not allow their sincerity to go to waste.