A popular saying in my alliance right now is "NO PC IN AC". This raises an obvious question: what does that mean? No personal computers in alternating current? No political correctness in air conditioners? That the speaker is abusing caps lock and therefore has nothing worth saying? And even those are assuming that one knows which of the pairs of capitalized letters are acronyms and which are not.
Of course, I've been in the alliance long enough to know that what it means is no price checks in alliance chat. But I've also been in the alliance long enough to know that it has a rule against price checks in alliance chat, without having to be told "NO PC IN AC" a few times per day. Rather, the people who need to see that are those who recently joined, and aren't aware of the rule. Those are the people least likely to understand the acronyms commonly used in their new alliance but not universally used throughout the game.
One who looks up PC on this wiki will see that it links to Price Check. But the abbreviations category lists no fewer than 307 abbreviations, and it's unreasonable to expect everyone in the game to just know that much jargon off-hand. As of this writing, AC isn't even one of the abbreviations listed.
Tragically, this can lead to people in some clique that uses particular acronyms a lot thinking that everyone uses those same acronyms. Those who don't recognize them are dismissed as stupid noobs or worse, primarily because they were merely in a different guild or alliance for most of their time in the game. In the case above, if as judged by wiki users, AC isn't one of the 307 most common acronyms, then it's not terribly reasonable to expect everyone to know it.
This is far from the only acronym abused, of course. SF seems to mostly mean Shadow Form. It used to mostly mean Searing Flames. Longer ago, it mostly meant Sorrow's Furnace. Google, meanwhile, emphatically insists that it means San Francisco. Hopefully one can see why using SF is rather ambiguous.
To this day, when someone talks about running to LA, I think, you can't run to Los Angeles from inside a fictional game! And there are many other DSFAs that players use.
The problem with acronym confusion does not lie with people who can't decipher some cryptic statement. Rather, it lies with people who overuse them instead of saying what they mean. If you use too many acronyms and someone has no idea what you're talking about, it's your fault, not theirs.
But how much use of acronyms is overuse? That depends some on whether you want people to understand what you're saying. If you're only talking to yourself, feel free to use whatever acronyms you want. You may wish to keep that out of channels where people will resent the spam, though. But let's create some rules for making abbreviations understood by the general public.
1. Something that looks like an acronym should really be an acronym. UW is not Underworld. UW is the University of either Washington or Wisconsin, or perhaps Wyoming. THK is not Thunderhead Keep.
2. If it needs a disambiguation page, don't use it. See, for example, the SF page above.
3. If it refers to one item out of a very large set (especially skills or locations), such that you wouldn't recognize acronyms for all of them, then don't use it. MS, for example, is the true acronym for at least 17 skills. If you're willing to drop the minor "of" in making acronyms, one can add two more skills to that list. Unless you can list all 19 of those skills without looking it up, using it to refer to one particular skill and expecting people to know what you mean is a terrible idea.
4. Acronyms should be long enough to have a high probability of being unique. Two letters is bad, unless it's something extremely commonly used. The name of a particular mission, skill, dungeon, or explorable area isn't used commonly enough. Three letters can still be problematic. Four or more letters is usually enough to make it unique. Having to type out two words instead of a two letter acronym does not take long.
5. Dropping words from names is only acceptable if the remaining words make it unique. Referring to a mission as "Sanctum", for example, could refer to either Sanctum Cay or Imperial Sanctum. Referring to a place as "Temple" could most easily be Tahnnakai Temple or Temple of the Ages, but a quick search of the wiki also turns up many other possibilities.
6. Only use acronyms that you can spell. This may perhaps mean that unusually bad spellers should refrain from using acronyms at all. Or better yet, that they should learn how to spell.
If speaking to a narrow audience and you don't care if the general playerbase would understand what you say, violating these rules is acceptable. If you do wish to be understood by the general public, violate these rules, and confuse people, it's your fault, not theirs.
I'm not against using abbreviations entirely, but they are best restricted to a small set. WTB or WTS in a trade channel are unambiguous, for example, largely because these are nearly the only two things that people do in a trade channel.
Oh, and in case you're wondering, DSFA doesn't stand for anything.