Agreed.
Typing the forum name of forum as bitcointalk.org forum, rather than any acronym or simply bitcointalk forum.
Because who knows in the future, crypto world might have bitcointalk.com, bitcointalk.ca, and some others similar sites.
I've mostly used BCT, though (while some may dislike it) I do think BTT rolls off the tongue pretty well (as well as being more distinct, at least when comparing it to the Bitcoin ticker symbol (BTC)). IMO BTCT is a bit too long of an acronym - once I've typed out more than 3 letters, I might as well type out the forum name in full.
Some opinions.
From what I've seen, "BTT" is only used by clueless bounty spammers. Real users refer to the site as BCT or just Bitcointalk if you're not too lazy to type
Honestly, I have read some bounty topic, that mentioned about BTT, or even in telegram or Discord channels.
At that time, around more than one year ago, I did not know what it means, honestly.
As @LoyceV pointed out, it tend to be used as BTT by lazy scammers, who even don't care which kind of forum they join to spread their scam projects out.
One more thing, when abbreviation BCT use, we should use it as BCT forum to avoid misunderstanding with any kind of tokens, altcoins launched later. Real crypto enthusiasts will easily known what BCT forum means.
It should be the best if we mention the forum as bitcointalk, the original, full name of it.
If someone are lazy to type down its full name, and if I have to make a vote, I will choose:
Bitcointalk forum, abbreviated as BCT forum.
I would prefer to spend a second to add the word 'forum' at the end.
In the future, there will be something, digital assets, or sites, or stocks, etc. that have its abbreviation, ticker as BCT, BCTT, BTT, so adding the word 'forum' at the end, after the abbreviation always make sense.
In short, I voted for:
BitCoinTalk forum ~ BCT forum.
We need the word 'forum' behind because for people who see or hear about the forum the first time, they don't know that bitcointalk.org is a forum. So, without the word 'forum', they might guess that it is a site, a marketplace, or something different than a forum.
To sum up, the best option (in my opinion) to write or call the forum is:
Bitcointalk.org forum.