When you double-click, say, the word "double-click", do you expect to highlight either "double" or "click", depending on which part of the word I happened to click on? Or do you expect to highlight the entire compound? Does your expectation change when the phrase is written with spacing: "double click"? When written without spacing: "doubleclick"? Does your perception of the word boundaries change between these cases?
Now consider another anglophone arbitrarily; how likely does it seem to you that they would share the exact same set of expectations of the above with you? Because if they don't, then one of you is going to have their expectations violated.
Now give it a try: do the highlights match your expectations? (Moreover: are those expectations consistent with where you placed the word boundaries?)
If your expectations of what double-click highlight does for English is consistent with what actually happens when you double-click, it is deeply unlikely that the causality goes word boundary -> highlight expectation; if they do, it's more likely that double-click highlight has influenced your sense of word boundaries.
But it's even more likely that you your expectations of double-click highlight don't actually match up with your intuition for word boundaries, and you just have a pretty good model of how double-click highlight behaves independently of where you think the word boundaries are.
(The notion of word boundaries in this context is fraught anyway. Even setting aside the problem of compound words, the phonological word boundaries of Japanese don't match up with the lexicographical ones, in both directions.)
I agree, there's definitely flexibility in what I expect, and what other people will likely expect. Here's the thing though: when I double-click "double-click", I could reasonably expect "double" "click" or "double-click" would be selected. I wouldn't expect it to select everything between the last and next punctuation characters (as an imperfect analogy).
For me at least, double-clicking is like fuzzy string matching. It's an imprecise behaviour by nature, but should be designed to be useful. Firefox's behaviour in the case of Japanese, but especially Chinese, often isn't useful, not because it doesn't perfectly reflect linguistic expectations, but because it usually selects too much--meaning you can't correct your selection by moving the cursor back and forth, and instead, have to stop and select using a different method.
Take the following passage:
もうこんなことは終わってほしいと願うばかりだ
Different people may break apart もうこんなことは differently, but it's hard to argue that it's one word. Chrome (and Word) separate it like this: もう こんな こと は, and whether or not you agree that each one of those parts are words, simply splitting もうこんなことは into parts semi-logically makes it smoother to edit (for me, at least! I understand most people might not be as dependent on double-click selection).
The same behaviour for Chinese is so useless that it's not even worth mentioning, since you'll always select either a large part of a sentence, or an entire sentence at once. I mean, I love the word 匹配的近似度用如下方法来度量.
Now consider another anglophone arbitrarily; how likely does it seem to you that they would share the exact same set of expectations of the above with you? Because if they don't, then one of you is going to have their expectations violated.
Now give it a try: do the highlights match your expectations? (Moreover: are those expectations consistent with where you placed the word boundaries?)
If your expectations of what double-click highlight does for English is consistent with what actually happens when you double-click, it is deeply unlikely that the causality goes word boundary -> highlight expectation; if they do, it's more likely that double-click highlight has influenced your sense of word boundaries.
But it's even more likely that you your expectations of double-click highlight don't actually match up with your intuition for word boundaries, and you just have a pretty good model of how double-click highlight behaves independently of where you think the word boundaries are.
(The notion of word boundaries in this context is fraught anyway. Even setting aside the problem of compound words, the phonological word boundaries of Japanese don't match up with the lexicographical ones, in both directions.)