Commonwealth English (question for Canadian, Australian posters & so on)

[Mr. Smith]

American, but I'm answering anyway.

Yeah, we Americans DO use the perfect tenses [your example is the present perfect]...it's just that we tend to prefer using contractions rather than say it longhand. "I've done"/ "I have done".

I do wonder if the preference for present perfect over preterite is an East v. West thing, as that divide seems to exist with Spanish dialects too [I flee to the Spaniards side just because it means fewer conjugations to remember, but I digress], but I'm not sure if Quebecois French vs France French has that difference...and I know the latter also tends to use present perfect more.

Another good one you missed though:

counterclockwise/anticlockwise

[Mr. Smith]

I generally use American grammar rules in more or less all circumstances, except for the past tense of "to spell" being spelt as..."spelt." "Spelled" sounds unnatural for some reason.

Spelt is a type of bread.

[Mr. Smith]

"Faucet" isn’t universally used.  "Tap", especially when describing the water coming from it, is just as common (if not moreso?).

I’ve noticed the British have a lot more positive adjectives in common usage when reacting to something, either genuinely or sarcastically.  "Brilliant!" "Lovely!" "Fabulous!" "Wonderful!" "Marvelous!"

If Americans use any of those it sounds weird, forced, or just out of place.  So we just stick to "awesome!"… and that’s about it.

Actually, besides "awesome" you can almost be assured those same adjectives would be used sarcastically only.

[Mr. Smith]

Apparently it's now standard in the scientific community to spell "sulphur" as "sulfur".  Abominable.

This is outrageous and it's things like this that make me distrust science.  How can I take what they say about global warming seriously if they can't even spell one of the most common elements?  Truly shocking.

Sulfur is objectively more sensible that sulphur because English is germanic language, not Greek, goddamit...

Having said that, aluminum just sounds like you have a speech impediment

I still mostly use British English because American English just sounds weirdly awkward and staccato. Just my perception.

Says the dude with Swiss German instead of Hochdeutsch and the infamously staccato Italian.

[Mr. Smith]

The primary grammatical difference I observe between American and British English is that British writers seem to be allergic to the subjunctive and will go to great (and, to an American eye, often ungrammatical) lengths to avoid using it.

Eh, subjunctive is a rather annoying tense anyway. It seems to be one of the few cases where American English takes the more esoteric rather than simplistic option.

[Mr. Smith]

The subjunctive is not a tense.

The primary grammatical difference I observe between American and British English is that British writers seem to be allergic to the subjunctive and will go to great (and, to an American eye, often ungrammatical) lengths to avoid using it.

Not in English anyway.

True to an extent, though I'd note that you are more likely to see the subjunctive mood expressed with "should" as in "he thought it important that they should return."