Markdown quote rendering fails when using full Matrix ID handles. In Element X

### Steps to reproduce

Open a chat in Element X.
Send a message with a quote containing a full Matrix ID: `> @user:matrix.org`
Compare the result by sending a markdown quote with a display name mention: `> @[User Name]`

### Outcome

In Element X, a message containing a Markdown quote renders correctly if the user mention uses the display name format (`@[Display Name]`). However, including a full Matrix ID (`@nickname:homeserver.abc`) within the quote syntax causes the entire message event to fail or render incorrectly.

#### What did you expect?
Expected Result: Both mention formats should be rendered correctly within the blockquote.

#### What happened instead?
Actual Result: The message containing the full Matrix ID within the quote breaks the message event.

### Your phone model

Samsung Galaxy S24 Ultra

### Operating system version

Android 16

### Application version and app store

Element X version 26.03.2

### Homeserver

Synapse 1.148.0

### Will you send logs?

No

### Are you willing to provide a PR?

No