I sympathise with those for whom their participation in the service is restricted by their ability to read/pronounce certain words, but it seems to me that this is a near-ideal chance for them to develop those abilities."

Church is a place where people should be able to forget the demands of the material world and search for inner peace. People who never learned to read right or who are in a foreign land get enough day-to-day frustration without coming to church and finding that they cannot join the others in song.

Those who point out that 'ph' (to name one example) is only one sound are ignoring the needs of poor readers, who find themselves wondering what to do with the p in 'tchphr'. (That's the middle of 'catchphrase.' We seem to get getting more poor readers all the time, so...

Editing out these unpronounceable clusters is not something I do often, because they don't occur often. Most people instinctively avoid them.
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Dave, thanks for your list. McGrath, how right you are!