UK-centric discussion follows.
I note some discussion here: http://www.sotawatch.org/reflector.php?topic=5329#44256 regarding the correct suffix to use. This is something I have had problems with. Not with knowing which suffix to use, which I am quite sure of, but with other people not knowing what they mean.
I think most of the problem is with people remembering the rules when they got their licence and not bothering to read the latest version. Please read it.
In summary, you are mobile if you are able to move and portable if you are somehow tied down, e.g. using a mast pegged to the ground.
I have already written about “mobile” here: http://mm0hai.net/radio/mobile.html
perhaps I should add comments on portable. It’s not something I enjoy having to debate (at all) but better here than when freezing on some summit. People have dragged me into this before when all I wanted was to get some entries in the log and get down.
If my interpretation is wrong please correct me but provide references, not comments to the effect, “I’ve always done it that way”.