Dipping into Gnomish again there is nafol “suspicious”, most likely from the early root NAVA.

http://eldamo.sourceforge.net/content/words/word-3632887323.html

Since V was not a phoneme used in Tolkien's later conception of Primitive Elvish, you would need to modify the root to either NAB- or NAW-. A root NAB- would produce forms like S navol.

Also, S fel- isn't completely outrageous. There is an attested root PHEL having to do with emotions which could have produced this Sindarin word:

http://eldamo.sourceforge.net/content/words/word-2238892409.html

I created that for my dictionary, so if that's the source you're taking about you could have just asked me where it comes from! :-) (If not then hey we both had the same idea from the same source). I'll give you the origin later when I'm back on my PC and have the files to hand.

For the various sentiments, Gnomish used impersonal expressions with individual verbs (e.g. luista nin "I am/*feel thirsty"), so maybe sentences like *defnada/demmada/níranna nin X "X grieves me, makes me (feel) sad" would be plausible or even to be expected in (Neo-)Sindarin.

Right, origin for the reconstruction:
felmë from VT41:19 suggests a verb fel- 'to feel' which comes from, as +Paul Strack points out, from the root PHEL.

+Jenna Carpenter Yes, it is your dictionary, I just now realized that. I downloaded it quite a while ago and on that site, there was no mentioning of any Carpenter as far as I can recall, but now I know! I'll rename the file Carpenter's dictionary, and so avoid future shortcomings.

"On the other hand I have heard of ways of expressing feelings like "my heart tells me ..." or "my heart is with you" or "it seems like ...( even ifmay not  be true)", and I'm sceptical and suspicious about that neologism."
If you mean the guren bed enni etc. expressions, they're Tolkien's own

It was fel- I was sceptical about, before I had the root PHEL shown to me. I wonder, do naf- and nafol have to undergo changes to be sindarinized?

+Hjalmar Holm If you accept the root NAB and posit primitive forms *nab- and *nablā, I think the only thing you need to do is revise the spelling to S nav- and S navol.

+Paul Strack Good!

+Paul Strack Is navol the present tense participe of the verb nav-? Would it not in that case rather be expected as navel? Or nava- as the verb?

Well, G nafol might be an active participle, but then it would mean "suspecting" instead of "suspicious", which is not quite the same. I think S navol could simply be an independently derived adjective.

I've seen fel- used a lot over the years by a lot of different Neo-Sindarin and Neo-Quenya translators. Anyone know if there's an origin, or it's just something that a lot of people came to the same conclusion on?

I usually use Guren bêd enni for expressing one's conscience or feelings/intuitions that one has about a specific topic, and adjectives to express certain states of being, unless there's a verb that covers the meaning.

So, for "I feel angry" I'd usually translate it as "Ni rúthui" (I am angry) or "Ruthron" (I rage/am raging), but if I want to say, "I feel like I know you" I'd translate it "Guren bêd enni i len iston." (My heart tells me that I know you.)

+Fiona Jallings yes, the noun felme "emotion" is attested in VT41

No, I mean who started using Fel- as a verb in Neo-Elvish translations? Who made the reconstruction? Or do we not know anymore?

+Fiona Jallings You should perhaps talk to +Jenna Carpenter , see earlier in this thread.

She's talking about the -me suffix, a common nominalizer of verbs in Quenya. I'm curious because if we know the origin, then we could add it to our Neo-Elvish dictionary. I like citing sources. :)

I think I saw the roots and thought 'that makes sense that's probably the verb' (or at least a decent idea of one), so it's in my lists because I came up with that, but I imagine it's one several people saw and thought the same thing about so I certainly wouldn't claim to have invented it or anything, and fairly sure I've seen it used by other people too.

"felmë noun "impulse, emotion" (VT41:19; this suggests a verb +#fel- "to feel"). Compounded in fëafelmë, hroafelmë"
This has been in Helge's wordlist for a long time, certainly for years now

Well that's Quenya not Sindarin but aye, exactly