Thorsten Renk has only been studying Elvish for about a year now, and has a bit to learn.  
He seems to want to proclaim that he is some sort of authority on Sindarin, but one only has to read this thread: www.councilofelrond.com/modules.php?op=modload&name=XForum&file=viewthread&tid=21467
to see that if it wasn't for CoE, he wouldn't even know that "an" was rather a Quenya intensifier. 

Here is my answer to his Elfling post.  His words are pasted in <<<< >>>>. 

<<<< ..... but words derived from intensified CE roots carry i-affection through all vowels including the intensification).>>>>
I don't think he could show us an example other than "Ithil" which normally has an "i" in it. I've shown examples of intensification for all vowels, and none show i-affection.  

<<<< ae_ in _daer_ is nothing but a strong vowel grade of _e_, there is  
no problem in principle - a prefix _e-_ could just reduce the vowel grade >>>>
That is his theory .... but I would say that Tolkien decided to intensify the Noldorin different than the Quenya word for "man".  "Doer/daer" (bridegroom) is most likely a vowel blend to show intensification of "dîr" (man) .... just like "glœr/glaer" (long lay) is shown to be the intensification of "glîr" (lay).  "Glîr" doesn't come from a base with an "e" in it, so his theory falls apart.    

<<<< we see from e.g. _einior_ (PM:358) that a word like _iaur_ containing a diphthing can receive a prefix while the 'base vowel' changes grade. Well - there are many reasons why Tolkien may have rejected a given form...>>>>
No, this is definitely a form using the "A" prefix with "N", not a base vowel prefix.  We discussed this on the thread above. Hmmm ... what is a diphthing ??  (I'm only asking because Thorsten doesn't seem to be able to tolerate anyone else's typos.)

<<<< There's plenty of evidence that Tolkien derived intensified forms in the Etymologies directly from CE roots.>>>>
No, the fact that he deleted "enner" is plenty of evidence to the contrary. The entry N "Udun" vs. Q "Utumno" under TUB is also evidence to the contrary. otherwise they would be practically the same. I'd use some words beginning with "a" as examples, but we can't be sure whether or not they are derived from "prefix A". 

<<<< First, the fact that _aññol_ appears listed under A- (VT45:5) and under N- (VT45:36) along with ÑOL (VT46:6) and not under O- suggests that it is actually an example for the A-/N- prefix, not for a prefixed root vowel, regardless of the emendation. >>>>  
No argument there ... I wasn't talking about the earlier version.

<<<< Second, Tolkien's own  derivation seems to be _oññol > ongol_  in parallel with the doubling seen in _apparkâ >  afarch_ (VT45:5) - so it doesn't seem to be _?o + ngol > ongol_. >>>>
It isn't.  That was his mistake when he thought "angol" was "an" + "gol" in our CoE thread. It's "o + ññol" = ongol.
Patrick Wynne's words are: 
"Both N angol and its intensive antecedent aññol  appear to have had their initial vowel subsequently altered, possibly to ongol and oññol respectively." If it is hard for anyone  to follow Mr. Wynne's explanation, it is simply ....
angol > ongol
aññol > oññol .... NOT oññol > ongol.  
"Subsequently" means "later" ... so "ongol/oññol" are the more recent forms.

<<<< With regard to the A-/N- prefix, CoE offers the example "_naur_ > _a + nnaur_ > _Anor_ (flame/fire > great flame/fire)" This interpretation likewise has problems. First, the capitalization (if not the translation) suggests that this is the derivation of _Anor_ 'sun' - but that is derived by Tolkien from an intensified CE root ANÁR (LR:348). And second, intervocalic _nn > n_ in Sindarin doesn't usually occur, so one would end  
up with _*annor_.>>>>
If you look under NAR you will find "Anor".  It is also under ANAR because ANAR is a derivative of NAR.  

<<<<  The author doesn't seem to be quite sure as to how dynamic lengthening  
works  .... I can help. >>>>
I hope people who read this post of his don't take Thorsten too seriously, as I go by attested examples (that's what I research) unlike his examples of .... 
kk -> kkh
pp -> pph
tt -> tth
 .... of which he says "those clusters will later become ch, ph and th in Sindarin". 

Normally, maybe ... but we are talking about "dynamic lengthening" here.
The only one he got right is "tt > th".  
Attested examples to counter his article are a + pparch = afarch, a + cc(kk)ar = agor, also a + mbarat > amarth for the nasal section..... do I need to go on?  Sindarin goes opposite to Quenya when you are dealing with nasalized stops.  That's why you have Q Turambar vs. S Turamarth.

 
Also to counter other statements:

<<<< For example, _n > nn > n or nd_ cannot stand - intervocalic _nn_ doesn't  
vanish, and intervocalic _nd_ is changed to _nn >>>>
Well, then we would need an explanation for "mindon", "randir", "Mindoluin", "Baranduin, and "nínim" (nîn + nimp) "white tear" 


<<<< c > cc > g_ cannot stand as _cc_ yield _ch_ in Sindarin/Noldorin, cf.  _rokkô > roch_ >>>>
Well, then Tolkien himself must have been wrong, as he used this for "agor" and "agarwaen".