Small and incorrect, that is.
This isn’t wrong when used as a noun (She sent a bottle of wine as a thank-you) or as an adjective (That thank-you bottle was much appreciated).
It is wrong when you are using the words to thank someone, as I saw in an e-mail recently: Thank-you for your help.
In that instance, Thank you is just a truncated version of I thank you, and no hyphen is necessary (or correct) in that kind of short sentence.
Fear and loathing?
This was the opening to a recent e-mail bulletin: I was loathed to admit …
OK, if by that the author meant he was detested – but that was clearly not the intention.
Auto-correct could be at work here, since many people say (and write) that they are loathe to do something (pronounced to rhyme with clothe).
That’s wrong too, though; the correct word is loath, sometimes (historically) spelt loth. They rhyme with growth and mean ‘unwilling, reluctant’.
Feedbacks and softwares
Like learning and training, these should never be pluralised.