Typographica "backticks" are actually accents as used in French and other languages. Like à for example. On a Mac keyboard (European) they are left of the backspace key. Hit that key plus pressing SHIFT and then hit SPACE. Otherwise they don't appear. Normally they are used to add an accent to a normal character.
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The call is still wrong. The first parameter must be the album folder name not the title. The title can be "album1" while the actual name on the filesystem can be "album2".
Also if the album is a subalbum of an album named "topalbum2" then the name of the subalbum is "topalbum2/album2".
$albumObject->getTags() will return you an array of tags for the album. Presuming you do not want tags that are not associated with albums you would have to make a loop that recursively goes throught albums/subalbums and retireves the tags, then filter out the non-unique values.
I edited your post, it was missing the closing backtick. They are like quotation marks, two are needed.
I took a look at the function. There are indications that an empty album name should mean something, but in fact all that seems to happen is that it does an SQL search for folders with no name (not a likely match.) You might try setting the second parameter to true, that will give something different, but maybe not any more useful.
Acrylan will have to comment on this when Germany wakes up in the morning.
First, if you pass a variable as a parameter like the dont use quotes...that will pass the variable name as text...
For the older questions: The plugin is not meant to be used without an album name passed. It only gets tags from a specific album (or its images) optionally including the subalbums of that specific album. Not tags from all albums and not for the album and all of its images.
With the css you have to figure that out yourself, sorry. Or look at the standard themes how they print a tag cloud on their archive.php page.