Ironically I really have no idea how to format this post, so mods feel free to edit the heck out of it.
These are the things I’ve been able to figure out. I googled BBCode commands, which seem to work, though in some formatting cases there are simpler shortcuts which I was able to guess. There are also of course buttons at the bottom of the comment window for Header text, Bold text, Italics, Quotes, Links, Code, Bulleted Lists, Numbered Lists, and Tags, but I’ll include the perhaps redundant BBCode formatting here for the sake of being thorough.
spoilers = double pipes ( || ) on either side of text, spaces OK; e.g.
||text||; alternate formatting
expandable “details” tab = put
>! in front of some text (click below for example); great for spoiler-tagging large blocks of text and images, especially as it conserves space in threads
For multiple paragraphs under one Details tab, double line break and
>! before every paragraph (this will not create multiple Details tabs). Thanks @saddleblasters
bold = double asterisks ( ** ) on either side of text, no spaces (** text **)
—>alt. bold = [ b ]text[ /b ] (spaces within brackets are for examples only; not case-sensitive)
italics = single underscore ( _ ) on either side of text, no spaces (_ text _)
—>alt. italics = [ i ]text[ /i ] (follows bold formatting rules)
underline = [ u ]text[ /u ] (“ ”)
strikethrough = [ s ]text[ /s ] (“ ”)
superscript = caret ( ^ ) before text, no spaces; can be applied to a string of paranthetical text
subscript = tilde ( ~ ) before text, no spaces; text strings work with parenthesis; can be stacked to achieve frighteningly small text
size = [ size=x ]text[ /size ], no spaces within brackets, 0 ≤ x ≤ 39
color = [ color=x ]text[ /color ], no spaces within brackets, color names or hex code
link to list of colors
direct tagging = @username
quote = >text, angle bracket must be at the margin, nothing to the left of it; line break twice to end quote
—> alt. quote (quote & reply) = highlight user’s text with cursor, small button saying “Quote” will appear; click to format highlighted text as quote within comment
fractions = x/y, where x and y are both single-digit integers or y is 10, x is less than y, and x and y do not share a common denominator; x can be negative.
Known auto-format fractions: ½, ⅓, ⅔, ¼, ¾, ⅕, ⅖, ⅗, ⅘, ⅙, ⅚, ⅐, ⅛, ⅜, ⅝, ⅞, ⅑, ⅒
don’t work: 2/7, 3/7, 5/7, 6/7, 2/9, 4/9, 5/9, 7/9, 8/9
horizontal bar = three underscores ( ___ ) at left margin
SO MUCH FUN THEY TAKE UP MORE SPACE
hyperlink = [ text in brackets ]( link in parentheses )
bulleted list = at beginning of line: hyphen, space, TEXT
line breaks stay within bullet margins
double line break to return to original margin
numbered list = at beginning of line: number, period, space, text
header text = text, line break, hyphen at margin