Excellent forensic approach. Let's examine these practices based solely on what the text actually states.

**Communion Analysis**

The modern Christian practice of communion involves:
- Weekly or monthly partaking of bread and wine/juice
- Viewing it as a sacrament or ordinance
- Often performed during Sunday services

However, examining the biblical texts:
- Matthew 26:26-28 occurs specifically during Passover meal preparation (Matthew 26:17-19)
- The "cup" mentioned is the Passover cup of blessing
- Paul in 1 Corinthians 11:23-26 is referencing this same Passover context
- The phrase "as often as" (Greek ὅσάκις ἐὰν) in verse 26 refers to the Passover timing, not arbitrary frequency

Biblical evidence for frequency:
- Passover was annually commanded (Exodus 12:14, Leviticus 23:5)
- Jesus kept it annually (Luke 2:41-42)
- Early believers continued annual observance (Acts 18:21, 20:6, 20:16)
- No command exists for weekly/monthly observance
- The "as often" refers to the annual recurrence of Passover

Forensic conclusion: The biblical evidence supports only annual observance aligned with Passover timing, not the weekly/monthly practice that developed later.

**Palm Sunday Analysis**

Modern practice: Celebrates Jesus' triumphal entry into Jerusalem occurring on Sunday before crucifixion.

Biblical evidence: 
- Recorded as historical event (Matthew 21:1-11, Mark 11:1-11, Luke 19:28-44, John 12:12-19)
- No command for annual observance
- No apostolic precedent for celebration
- Simply records what happened that particular Sunday

**Good Friday Analysis**

Modern practice: Commemorates crucifixion on Friday.

Biblical evidence:
- Crucifixion occurred on preparation day before Sabbath (John 19:31,42)
- No command for annual observance
- No apostolic precedent for celebration
- The timing is actually problematic given Jesus' "three days and three nights" prophecy (Matthew 12:40)

Forensic conclusion: Both Palm Sunday and Good Friday are post-biblical traditions without direct scriptural support for liturgical observance. They record historical events but lack commands or precedents for becoming annual holy days.

The evidence suggests these practices developed centuries after the apostolic period as church traditions rather than biblically mandated observances.