Terminal underlines URL addresses on the screen. An accident mouse click on the addresses, for example on selecting a text, causes an undesirable start of a browser. I propose the option to switch off this feature. I use Terminal-0.4.2 and vte-0.22.3.
This action only happens with Middle click or Right Click > Context menu > Open link. Can you verify? otherwise you might have a bug not a feature :p
It occures both at Middle click and Right Click > Context menu > Open link. In the second case "Open link" is the first in the context menu, it could be selected accidentally.
I don't consider middle click as accidental, not very harmful either.
Middle click is used for insertion of a text into cursor position. You may click the middle button anyway inside terminal window and text is inserted at cursor position. It is the common feature of various terminal emulators (e.g. xterm). Sometimes accindentally such the click occures over highlighted links. On these occasions Terminal executes browser instead of pasting the text.
I nearly forgot there is a hidden option in the rc file: MiscHighlightUrls. If you set this to FALSE the terminal won't handle urls. I find this too uncommon to create an option for it in the configure dialog.