Add mention of non-support for slack threads for /security cmd

content/handbook/security/security-operations/sirt/engaging-security-on-call.md

@@ -28,7 +28,7 @@ The following items are out of scope for SIRT and should be escalated to the res
 
 For general Q&A, GitLab Security is available in the `#security` channel in GitLab Slack.
 
-For low severity, non-urgent issues, [SIRT](/handbook/security/security-operations/sirt/) can be reached by mentioning `@sirt-members` in Slack or by opening an issue with `/security` in Slack.
+For low severity, non-urgent issues, [SIRT](/handbook/security/security-operations/sirt/) can be reached by mentioning `@sirt-members` in Slack or by requesting the incident form link, using the `/security` slash command in Slack. (Note: this command does not work inside Slack threads)
 
 Please be advised the SLA for Slack mentions is **6 hours** on business days.
 

content/handbook/security/security-operations/sirt/sec-incident-response.md

@@ -7,7 +7,7 @@ controlled_document: true
 
 ## Purpose
 
-The [Security Incident Response Team (SIRT)](/handbook/security/security-operations/sirt/) is on-call [24/7/365](/handbook/engineering/on-call/#security-team-on-call-rotation) to assist with any security incidents. If an urgent security incident has been identified or you suspect an incident may have occurred, please refer to [Engaging the Security Engineer On-Call](/handbook/security/security-operations/sirt/engaging-security-on-call/) and use the Slack /security command by going to a new message thread anywhere in Slack, typing the following command and pressing enter:
+The [Security Incident Response Team (SIRT)](/handbook/security/security-operations/sirt/) is on-call [24/7/365](/handbook/engineering/on-call/#security-team-on-call-rotation) to assist with any security incidents. If an urgent security incident has been identified or you suspect an incident may have occurred, please refer to [Engaging the Security Engineer On-Call](/handbook/security/security-operations/sirt/engaging-security-on-call/) and use the Slack /security command by writing a new message to either yourself, or a public/private channel in Slack (this command does not work inside Slack threads), typing the following command and pressing enter:
 /security
 
 Information about SIRT responsibilities and incident ownership is available in the [SIRT On-Call Guide](/handbook/security/security-operations/secops-oncall/).