A very enjoyable puzzle from Goliath.
Nothing too tricky and a good mix of clue types going on in the grid. 14d was a new word for me. Lots to like, so many thanks to Goliath!

ACROSS
1. Desperately dreads becoming even more miserable (6)
SADDER
4. Birds roll about on board (8)
SWALLOWS
WALLOW (roll about) on board (on SS, steamship)
9. Abating and stopping, not starting! (6)
EASING
[c]EASING (stopping, not starting)
10. What may follow beatification is recited mantra including religious text (8)
SAINTDOM
(SAID (recited) + OM (mantra, sacred syllable of Hinduism)) including NT (religious text, New Testament from Christianity)
12. Seems that themes can be heard in this speech (4)
LISP
Cryptic definition
Someone with a lisp might pronounce ‘seems’ as ‘themes’
13. An unusually sane and healthy author (4,6)
ANNA SEWELL
AN + SANE* (*unusually) + WELL (healthy)
15. Piles of horrid homes to welcome a renovation (12)
HAEMORRHOIDS
(HORRID HOMES)* to welcome A (*renovation)
18. I’m no intellectual, therefore I see things differently (1,4,5,2)
I DON’T THINK SO
I DON’T THINK (I’m no intellectual) + SO (therefore)
21. For reign to get renewed, find the ancestor (10)
PROGENITOR
PRO (for) + (REIGN TO)* (to get renewed)
22. Our duty to preserve language (4)
URDU
[o]UR DU[ty] (to preserve)
24. Openings as an alternative, providing sweets (8)
ORIFICES
OR (as an alternative) + IF (providing) + ICES (sweets)
25. Doctor, setter, house of power (6)
MEDICI
MEDIC (doctor) + I (setter)
The House of Medici was a very wealthy and influential family in Italy during the 14th to 18th centuries
26. Park back in the times o’ yore (8)
YOSEMITE
[th]E TIMES O’Y[ore]< (in, <back)
27. Joiner spoken of in elevated lowland? (6)
HYPHEN
“HIGH + FEN” (elevated + lowland, “spoken of”)
DOWN
1. Pinch your secret (8)
STEALTHY
STEAL (pinch) + THY (your)
2/20. Sea storm I’d produced competes with Titanic and suchlike (8,6)
DISASTER MOVIES
(SEA STORM I’D)* (*produced) + VIES (competes with)
3. Northerner capturing eagle (4)
ERNE
[North]ERNE[r] (capturing)
5. Amazing fight by solver! Now tell me your news (4,5,3)
WHAT ABOUT YOU
WHAT A BOUT (amazing fight) by YOU (solver)
6. Varnish 7 Nile bananas (7,3)
LINSEED OIL
(OLDIES (answer from 7) + NILE)* (*bananas)
7. The elderly soldier, mostly traumatised (6)
OLDIES
SOLDIE[r]* (mostly, *traumatised)
8/17. Easy answer could be brine (6,8)
SIMPLE SOLUTION
Double definition
Brine is salt dissolved in water, so scientifically a simple solution
11. Adamant and on the move, gathering information (12)
INTRANSIGENT
IN TRANSIT (on the move) gathering GEN (information)
14. In an empty bedroom, playing Wordle is a call for censorship (10)
BOWDLERISM
In B[edroo]M (empty); WORDLE* (*playing) + IS
16. Ask not a European to embrace Marxist leader, it’ll cause an altercation (8)
SKIRMISH
[a]SK (not A) + (IRISH (European) to embrace M[arxist] (leader))
19. Creepy broadcaster full of crap (6)
SPOOKY
SKY (broadcaster) full of POO (crap)
23. Times covering zero-emission car group (4)
BEVY
BY (times) covering EV (zero-emission car, electric vehicle)
A playful grid from Goliath with his usual bag of tricks. I had lots of ticks including LISP, SPOOKY, STEALTHY, SKIRMISH and BOWDLERISM. There were more besides but suffice to say it was ‘piles’ of fun.
Thanks to him and Oriel.
Very enjoyable puzzle by Goliath. I especially enjoyed HYPHEN. Thanks Oriel for your usual great blog.
A fun puzzle and not as tricky as Goliath can be. I will confess to using the autofill for 15a – a word I can never spell correctly – but I knew what I was anagramming so I’m not taking that as a cheat! I thought YOSEMITE was brilliantly hidden, SPOOKY made me laugh and I enjoyed the quaint wording in SKIRMISH. BOWDLERISM was my only eyebrow raise – I thought the inclusion of ‘an’ was a tad unfair: the clue would have been the same without it – ‘In an empty bedroom …’ is no different from ‘In empty bedroom …’ so I assumed the ‘an’ had a reason to be there. When I returned to the clue with crossers, the solution was clear but left me slightly irritated.
Thanks Goliath and Oriel
A double treat today, with Philistine in the Guardian – and lots of fun, including the challenge of spelling 15ac unaided!
My ticks were for SAINTDOM, I DON’T THINK SO, OLDIES, EASY SOLUTION, SKIRMISH and BOWDLERISM (l had the same initial reaction as PostMark but I really enjoyed the clue).
Many thanks to Goliath and Oriel.
Liked LISP, HYPHEN, SIMPLE SOLUTION and BOWLDERISM.
Thanks Goliath and Oriel.
KVa @5. I initially made the same spelling error as you have 😉
😊
BOWDLERISM
Thanks Hovis!
Re 15A: Did anyone actually spell the word correctly without consulting a dictionary?
Last one in was 8/17 which I only worked out from all the cross letters. I didn’t really know what “brine” is.
Thanks Oriel.
Thanks Goliath for a super crossword as usual. My top picks were ANNA SEWELL, HAEMORRHOIDS (having 2 O’s & 1 E in the anagram fodder helped me spell this correctly), I DONT THINK SO, URDU, the expertly hidden YOSEMITE, and INTRANSIGENT. I failed with HYPHEN. Thanks Oriel for the blog.
I echo the positive comments about the puzzle. My favourites were URDU, MEDICI, YOSEMITE, JOINER, INTRANSIGENT (nice surface and nice misdirection), HAEMORRHOIDS, and PROGENITOR (LOI). A different list to others, which I think indicates there were a lot of good clues today. I felt there were a few filler words that got in the way of the parsing beyond 14d, but I did not think it a big deal.
Thanks Goliath and Oriel
I struggled at first but then all seemed to fail into place. Of the many enjoyable clues I particularly liked HYPHEN and LISP. Well done setter and blogger alike !
I thought lisp was great fun. Trying to go fast I guessed saline solution and messed up saintdom, and sewell! Oh well, thanks everyone,