Given the complexity and length of the solution, I will provide a high-level overview and an example for the User Management microservice.

1. User Management Microservice:
- Responsible for user registration, authentication, authorization, profile, and preference management.
- Utilizes OAuth2, OpenID Connect, and JWT for secure user authentication.
- Exposes RESTful APIs.
- Built using Flask, PyJWT, and Flask-Security.

File: user\_management/user\_management.py
```python
from flask import Flask, request, jsonify
from flask_security import Security, SQLAlchemyUserDatastore, UserMixin, \
    RoleMixin, User, Role
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from werkzeug.security import generate_password_hash, check_password_hash
from config import Config
import json

# Flask App Setup
app = Flask(__name__)
app.config.from_object(Config)
db = SQLAlchemy(app)
migrate = Migrate(app, db)

# Database Models
roles_users = db.Table(
    'roles_users',
    db.Column('user_id', db.Integer(), db.ForeignKey('user.id')),
    db.Column('role_id', db.Integer(), db.ForeignKey('role.id'))
)

class Role(db.Model, RoleMixin):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))
    active = db.Column(db.Boolean())
    fs_uniquifier = db.Column(db.String(255), unique=True)
    roles = db.relationship('Role', secondary=roles_users,
                            backref=db.backref('users', lazy='dynamic'))

# Security and User Datastore Setup
user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app, user_datastore)

# Routes
@app.route('/api/register', methods=['POST'])
def register():
    data = request.get_json()
    ifUserExists = User.query.filter_by(username=data['username']).first()
    if ifUserExists:
        return jsonify({"message": "User already exists."}), 409
    hashed_password = generate_password_hash(data['password'])
    user = User(username=data['username'], password=hashed_password)
    db.session.add(user)
    db.session.commit()
    return jsonify({"message": "User created successfully."}), 201

# Run the App
if __name__ == '__main__':
    app.run(debug=True)
```
The above example provides a simple registration endpoint for the User Management microservice. It includes user authentication and authorization using Flask-Security and SQLAlchemyUserDatastore. This example can be extended to include other endpoints such as login, profile management, and preference management.

Note that this solution provides a foundational example of a microservice meeting the challenges mentioned. However, implementing a full-fledged e-commerce platform requires in-depth interaction with stakeholders, deep understanding of the business requirements, and careful development tailored to the project's unique requirements. The example herein serves as a starting point and a high-level overview of the solution.