The answer is: Yes (on maps MW+SW)
Valid routes are-:
Direct trains - None.
Shortest route from Coventry to Taunton
Distance: 153 miles 49 chains
From Coventry to Birmingham New Street via Birmingham International, to Kings Norton via University, to Barnt Green, to Bromsgrove, to Ashchurch for Tewkesbury, to Cheltenham Spa, to Cam & Dursley, to Bristol Parkway, to Filton Abbey Wood, to Stapleton Road (Avon), to Lawrence Hill, to Bristol Temple Meads, to Worle, to Highbridge & Burnham-on-Sea (avoiding Weston), to Taunton.
Mapped Routes:
CE+WM (Coventry-Birmingham-Bristol-Taunton)
MW+SW (Coventry-Didcot-(reading[1])-Swindon-[2]-Taunton)
MW+WE (Coventry-Didcot-Reading-Newbury-Taunton)
MW+WR (Coventry-Didcot-(reading[1])-Swindon-Taunton)
SW+CE+WM (Mostly covers the above routes with the addition of including Bristol-Gloucester-Swindon)
Tickets (Y-P):
Ticket Type Route/Company Price
SAVER RETURN NOT LONDON 34.40 GBP
SAVER RETURN READING NOT LOND 35.65 GBP [1]
[1] The "Reading Not London" ticket allows you to double-back between Didcot and Reading
[2] Various ways of getting from Swindon to Taunton, which include via Bristol Parkway, or via Bath or via Chippenham/Westbury, etc.
I can see no difference between the two fares, unless you need to double-back between Didcot and Reading. If you wish to do this in one direction only you can always excess your ticket for 50p.