Read repair implicitly increases read timeout value

When read repair occurs during a read, internally, it starts several blocking operations in sequence. See org.apache.cassandra.service.StorageProxy#fetchRows. 
The timeline of the blocking operations

1. Regular read, wait for full data/digest read response to complete. reads[*].awaitResponses();
2. Read repair read, wait for full data read response to complete. reads[*].awaitReadRepair();
3. Read repair write, wait for write response to complete. concatAndBlockOnRepair(results, repairs);

Step 1 and 2 share the same timeout, and wait for the duration of read timeout, say 5 s.
Step 3 waits for the duration of write timeout, say 2 s.
In the worse case, the actual time taken for a read could accumulate to ~7 s, if each individual step does not exceed the timeout value.
From the client perspective, it may not expect a request taken higher than the database configured timeout value. 
Such scenario is especially bad for the clients that have set up client-side timeout monitoring close to the configured one. The clients think the operations timed out and abort, but they are in fact still running on server.