Annoying little quirks of text highlighting and navigation. Oopsie, you moved an extra quarter of a centimeter to the left of the paragraph you tried to highlight starting from the bottom. That means you want everything, right? Yeah we're highlighting everything. And so on.

Fortunately I've picked up some workarounds over the years:

Trying to highlight text in a hyperlink: hold alt

Methods of selecting text blocks (e.g., when normal mouse-select is doing bizarre stuff):

• Try highlighting from end to beginning
• Click point A, hold shift, click point B
• Double-click first word of desired selection to highlight it, or triple-click a paragraph, then highlight letters with shift-right, words with ctrl-shift-right, lines with shift-down, paragraphs with ctrl-shift-down. You'll see that, for example, when you use shift-down, some text on the line following the selected line is also selected, corresponding to the length of the initial selection before the hotkey was pressed. You can use relevant combos in the opposite direction to de-select this. Or press shift-end to highlight only to the end of the line where your current selection ends, and shift-home to deselect to the beginning of the line. Ctrl-shift-end/home will do the same but for the entire page/document.
• Some other useful hotkeys are available during text input -- I make heavy use of shift+pgup/pgdn to extend selections, but this seems to work in Excel, Notepad++, etc., not in this web browser text input field, for example. Holding shift while clicking also extends selections as in the read-only context; holding ctrl while clicking arbitrarily adds to selection just as in the file browser.