As a beginner I’ve gotten into the habit of tonguing everything and am trying to wean myself off by practicing tunes without any tonguing. But is it okay to tongue cuts? Does anyone do that for more emphasis? Come to that, does anyone tongue the cut part of a roll?
Yes, often. Soft or hard tonguing give different effects.
Yes, sometimes. The effect is of a note followed by an off-beat short roll.
Thanks MTGuru. So it sounds as though there’s a lot of leeway and freedom when it comes to tonguing or not tonguing. What do you mean by hard or soft tonguing exactly?
Tuh Tuh versus Duh Duh, roughly. But there’s lots of room for syllabic variation. For example, try Suh Suh, or Welsh Lluh Lluh. 
Coming to whistle from GHB, I did not tongue at all. On the rare occasions that tonguing seemed needed, I used a glotteral stop. It took some years bsrfore I began incorporating various types of tonguing into the techniques of articulation. As the OP is coming at it from the opposite side by tonguing everything, it seems it might be good to concentrate on not tonguing anything, unless there was no other way to articulate something. Using a glotteral stop might be a substitute there. I am assuming the OP is learning ITM. The habit of tonguing everything should be broken, and tonguing added back in after mastering legato technique.
Sorry, GHB?
Great Highland Bagpipes (Scottish pipes)
It’s fascinating to see how different articulations/embellishments/ornamentations are used and affected. I started off on the recorder where if you didn’t tongue everything someone would rap your knuckles for it. I learned then that the glottal stop was an effective way of softening transitions where the various T’s, D’s, S’s, L’s and such were either difficult to enunciate or ineffective. Now I rarely, or more precisely - never, use tonguing when playing whistles as I’ve become so accustomed to using various degree’s of glottal stop without even thinking about it. It’s a completely unconscious act. I just tried playing my high D Sindt while tonguing where I normally use glottal stops and it sounded terrible to me. I haven’t even thought about it until just now.
I have absolutely no judgment about the act of tonguing and can clearly see where it’s much easier to learn than a glottal stop. I’ll have to experiment with it sometime I guess.
I suppose my current technique would give me a leg up should I consider GHB. 
Of course, there’d be my marriage to consider then too.
ecohawk
I would have to certainly agree with MTGuru. Tonguing is certainly used in playing tunes on the tin whistle. I would suggest learning and memorizing the tune first (in a legato fashion, not tonguing every note) before you start any embellishments, such as tonguing. As you have been so used to tonguing each note, why not using this skill and try tonguing a triplet? I would suggest TWO-KAH-TWO’ing the notes: b(TWO), c natural(KAH), and d(TWO) as good practice. This is just one idea, and you will certainly hear some great examples of this style from Brian Finnegan, who is a beast at it! It is all personal preference, therefore, do not let anyone steer you one way or the other, as there are plenty of old and new recording consisting of players tonguing notes. Best of luck to you!
Thanks for all the comments. And it’s good to know I’m not doing anything particularly wrong right now. I like your suggestion Christelrice for learning a tune legato to begin with. Even though I’m trying to copy some of my favourite recordings, according to Brother Steve’s pages, it is good practice to play legato since it makes sure you are not covering up sloppy fingering changes. And I wonder whether it’s easier to memorise a tune (something I haven’t managed yet) by learning the notes first and adding ornaments later.
Ornaments can’t actually be removed from a tune. The tune without them, isn’t the way the tune should be.
Learn a new tune and try and put in any ornaments you know as you learn it.
You’ll learn the tune and practice the ornament too. Just don’t rush to learn all ornaments all at once. Concentrate on your cuts and taps first, getting them quick and accurate. They are the building blocks of life and tunes.
Everyone learns at different pace. Some folks are more comfortable learning the “bare bones” of the tune first, leaving the ornaments until they memorize the whole tune first. More skilled players are comfortable learning the ornaments while memorizing the tune. As you stated that you are new to memorizing tunes, I would suggest that you get comfortable playing the tune in a legato fashion first as you are memorizing it. My teacher, Mike Rafferty of East Ballinakill taught me this way, phrase by phrase in a legato fashion. Mike would play the ornaments as he taught each phrase of the tune, although it was more of an after thought than anything else. He always stressed the importance of playing the notes correctly. Tonguing each note can also compromise your ability to play in time once you pick up the speed. These are just my suggestions; I hope this is helpful!
Yes a mix of legato and staccato is best I feel for the whistle unless u really want a staccato/tonguing style like Sean Ryan for example. Its all about personal taste and style. I use tonguing sometimes as a variation for rolls and cuts. It is absolutely finr to tongue for cuts and rolls too.